Physics Test
to calculate tangential velocity
calculate angular velocity of axis of rotation and measure length of radius of rotation
motion
can be linear, angular, or general
stability
capacity of an object to return to equilibrium or its original position after it has been displaced, dynamic concept
what does center of gravity determine
center of gravity determines how the body responds to external forces, control
If an object moves with a constant acceleration, what is its velocity?
change by the same amount each second.
angular displacement
change in angular position, vector, θ theta
angular velocity
change in displacement/ change in time, vector, ω omega
angular speed
change in distance/ change in time, scalar, σ sigma
What is the combined speed of two identical objects that have a head-on collision in space if one is moving at 2 m/s and the other is moving at 1 m/s? (The objects stick together upon collision)
change in velocity = 2 m/s - 1 m/s = 1 m/s divided by 2= 0.5 m/s
Which experiences a greater air resistance - a bird's feather falling from a tree to the ground or a coconut doing the same?
coconut - has more force
general motion
combo of both linear and angular movement
What does a constant net force on an object produce?
constant acceleration
What does a constant net force on an object produce?
constant acceleration.
compensatory and intial movements
counter act each other to keep us stationary so we don't fall backward or lean forward
Voltage =
current x resistance
Charge =
current x time
Electrical Power =
current x voltage
sharper turn
decrease speed
bending limbs
decreases moment of inertia
decrease radius of rotation
decreases speed, more control, better aim
systematic approach of qualitative analysis
describe technique, observe movement of individual, evaluate performance, provide feedback and instruction to individual
qualitative analysis
described without numbers
linear kinematics
describes changes in position in space
angular kinematics
describes the spatial and temporal components of rotation, describes rotations in space
kinematics
description of motion taking into account position, rate and changes in state of motion
why we use angular distance instead of displacement
displacement, underestimates how far the system moved
Average Speed =
distance / time
What are the two necessary measurements for calculating speed?
distance and time
radius of rotation (r)
distance between axis of rotation and point of interest on a system
sagittal plane
divide body left and right
frontal plane
divides body into front and back
transverse/ horizontal plane
divides body into top and bottom
non linear relationship between muscular (linear) and joint movements (angular)
due to different properties of tissues in muscles and bones and the different muscles that act on a joint
third class lever
effort in the middle, fulcrum and resistance on either side, mechanical advantage is always less than 1
angular motion and 1st law
every body persists in its state of being rest or rotating uniformly unless compelled to change state by torque impressed
newtons third law and angular motion
ex: gymnast push down on springboard, force acts over a distance causing rotational force, reaction force propels gymnast up and into air creating rotation, counter torque is equal in magnitude and opposite in direction
local term
examining momentum of an individual segment of system
remote term
examining momentum of entire system
to be in balance, state of quilibrium
external forces acting on it or the moment of those forces must sum to zero
relationship between linear and angular motion
faster ball rotates faster in translates, more it spin further it travels
camera is in sagittal plane, mediolateral axis
flexion, extension, pitch
centripetal force
force exerted on the rotating object to cause radial acceleration
torque
force that has a tendency to rotate an object about an axis
external angle
formed on the exterior surface of the joint
direction of the axis of rotation
found perpendicular to plane of motion
first class lever
fulcrum in middle, resistance and effort on either side, mechanical advantage may be greater or less than 1
What does your weight displayed on your bathroom scale measure?
gravity's force on you
What would the maximum acceleration of a car be if it tows a 2nd car of the same mass?
half its original acceleration
Circular Motion—Tangential Speed
he distance traveled by a point on the rotating object divided by the time taken to travel that distance is called its tangential speed (symbol v). Points closer to the circumference have a higher tangential speed that points closer to the center.
inertia in frontal plane
high
to measure joint angle we need to
identify location of 3 joint centers of rotation, and the orientation of the 2 longitudinal segments
acceleration of angular body
if velocity changes, acceleration changes, if magnitude or direction changes then velocity is changing
free body diagram
illustration to visualize applied forces and resulting reactions, can determine effect of the forces on the system
increasing duration of torque application
increases change in angular momentum
increase radius of rotation
increases speed
less sharp turn
increases speed
increasing base of support
increases stability, wider feed are apart more stability vs standing on one foot decreases stability
affect of mass
increasing mass increases stability, more inertia (resistance to change), increase contact forces which increases friction
An object with twice as much mass as another object has twice as much what?
inertia
effort
input/ applied force
quantitative analysis
involves actual measurements, described in numbers
analysis
involves breaking something into smaller parts and examining them
direction of the linear movement
is on the tangent to the rotating object
radial acceleration of an object rotating in a circular path
is the component of linear acceleration directed towards the axis of rotation
What happens to the acceleration of an object when it reaches its terminal velocity?
it no longer accelerates it is zero
What happens when a rocket ship gaining speed in outer space runs out of fuel?
it will continue moving at the rate of speed it was going when it ran out of fuel.
What does a car tend to do if you release the brakes after slowing from 60 km/h to 40 km/h on the highway?
it would keep moving at 40 until resistance kicked in and slowed it down
What would the skidding distance be of a truck that has twice the mass of another truck?
it would stay the same, just increasing amount of friction
counter rotation
keeps body in stationary position
compensatory movement
kicking legs forward will cause the body to rotate backwards
observing movement
know who you're observing, know the conditions/environment (surroundings), what plane to observe, and what to look for (velocity, position, ROM), provide effective feedback frequently to reduce errors
newtons first law
law of inertia, every object has a desire to remain in a static state
newtons second law
law of momentum, creating a change in the state of motion (dynamic motion)
Which tennis ball will hit the ground first if 2 are dropped from a tall building and one of them is filled with lead pellets?
lead pellets
Why is it difficult to accelerate a car on a level surface on the moon?
less force but same mass
radius of gyration (k)
linear distance between axis of rotation to point where the body mass is concentrated
pitch
look up or down (nod yes)
inertia in transverse plane
low
lowering your body
lowers center of gravity
effect of torque depends on
magnitude of force, point of application, and direction
What does a kilogram measure?
mass
What does linear inertia depend upon?
mass
Why did a pulley stop spinning?
mass close to axis
why is it easier to move pencil in the middle than at the end
mass is closer to the axis
How does the mass of an apple on the moon compare with that on Earth?
mass stays the same
effectiveness of lever is determined by
mechanical advantage, ratio of output to input force, measured by distances between the forces and axis of rotation
camera is in horizontal plane, longitudinal axis
medial, lateral rotation and yaw
How does the GPE of an object compare if it is raised twice as high as before?
mgh, if h is doubled what does it do to the overall amount of GPE? Twice as much overall.
inertia in sagittal plane
moderate
perpendicular distance
moment arm
conservation of angular momentum
momentum in all instances are the same
What speed does a free-falling cantaloupe have 12 s after starting from rest?
more than 100m/s
angular motion is important because
most human movements are the result of angular motions
static equilibrium
motionless state
linear motion
movement along a line with all parts of the body moving in the same direction and speed
task sheet
movements is divided into phases, body is divided into segments, used to identify where the problem is in qualitative analysis to help individual with success
dynamic equilibrium
moving state
anatomical levers
musculoskeletal systems are mostly third class, arrangement of tissue amplifies speed and ROM generated by muscular effort
observation fro qualitative analysis
need to have knowledge of the skill, purpose/goal of skill, and understand most effective technique for success
clockwise rotation
negative values
In what units does one properly express the weight of an object?
newtons
center of gravity
not a physical entity, not marked on object, point in which a system's weight is evenly distributed or balanced, point through which the force of gravity acts
angular motion
occurs when all fixed points on an object move in circular paths about the same fixed axis
adding to a lever
only can add torques
absolute angular position
orientation of an object relative to a fixed reference line or plane
relative angular position
orientation of an object relative to another object or line
resistance
output force
how and where biomechanical measurements are taken affects
parameter being measured
technique determines
performance
moment arm
perpendicular distance between line of action of the force and the axis of rotation
center of gravity
point around which a systems weight is equally distributed in all directions
center of mass
point around which masses are balanced
counterclockwise rotation
positive values
radial acceleration (centripetal)
present when an object changes direction, the forces that causes radial acceleration to occur is directed towards axis of rotation, a = v^2/r
rectilinear motion
produced by force acting through center of gravity
curvlinear motion
produced by forced acting off the center of gravtiy
angular impulse
produces a change in angular momentum
couple
produces rotation
force
push or pull that can produce linear movement
angular momentum (H)
quantity of motion, consequence of motion, kgm^2/s, moment of inertia x angular velocity
angular motion and 2nd law
rate of change of angular momentum of body is proportional to the torque causing it and the change takes place in the direction in which the torque acts
radian
ratio between angle in circle and length of arc, 1 rad is 57.3 degrees
Why will a feather and a coin have equal accelerations when falling in a vacuum?
ratio of force to mass is the same.
What is the reaction force to pulling on the end of a spring attached to the wall?
reaction is the wall pulling on the spring.
digitization
representation of an object by a series of discrete points/markers
second class lever
resistance in middle, fulcrum and effort on either side, mechanical advantage is always greater than 1
axis of rotation
resting or pivot point of lever
angular movements can be described as
rotation
angular motion
rotation around a central line or point
torque is
rotational force, moment of force, moment, twist to an object
moment of inertia
rotational inertia, the resistance of any physical object to change in its angular state of motion, mass x (radius of gyration)^2, kgm^2
mediolateral axis
runs towards and away from the midline, rotation occurs on saggital plane, movements include: flexion , extension, hyper extension, pitch
analyzing human movement
seperate angular and linear motion for analysis
r
sharpness of turn, sharper turn = more force required
shifting of center of gravity
shift depends on weight of segments and the distance moved, if can shift up, down, forward, back, left, or right
adding weight to top of system
shifts center of gravity up towards the added force, heavier end
position of center of gravity
shifts towards the side which weight is concentrated on
What happens if you apply less force to a horizontally sliding object than is needed to maintain a constant velocity?
slow down and come to a stop
What did Galileo's use of inclined planes allow him to do?
slow down the acceleration of free fall. Galileo used inclined planes to slow down the ball's change in speed by changing the angle that the inclined planes were set at.
absolute angle
space between a body segment with respect of a fixed line reference, could be an angle measured between the longitudinal segment and y or x axis
relative angle
space between the longitudinal axes of adjacent segments, angle at a joint
What increases when an iron block near the earth's surface is in free fall?
speed increases
What are two factors that greatly affect air resistance?
speed of the object and frontal area size
affect of position of center of gravity
stability decreases as it moves towards the anterior posterior edge or lateral edge of base of support, decreases as it moves up, higher center of mass greater amount of torque its motion creates about the support surface, lower center of gravity more stable
equilibrium
state of physical balnace, in which opposing forces equal out
If gravity between the Sun and Earth suddenly vanished, Earth would continue moving in what path?
straight line path
angular kinetics
study of torques
initial movement
swinging the arm forward at shoulder joint will cause the body to rotate forward
rigid body
system being moved
electrogoniometer
taking measurements during movement, dynamic analysis
motion capture
technique that allows the study of key movements, important non movements and movement relationships
variables of quantitative analysis
temporal (time), kinematic (position, displacement, velocity, acceleration), or kinetic (force, energy, work, power)
if radius of gyration increases
than angular velocity decreases, ex: spreading arms apart in skating slows you down
Your weight as measured on your bathroom scale is *
the force due to gravity on you
newtons second law re examined
the law of acceleration
newtons third law
the law of reaction, every action has an equal and opposite reaction
Nellie hangs from a pair of ropes at an angle. What does the tension in the rope depend on?
the length of each rope and the angle the ropes are set at.
mechanical advantage decreases
the lever amplifies the speed & range of motion but sacrifices strength, a force can move a resistance arm through a large range of motion when the force arm is shorter than the resistance arm
mechanical advantage increases
the lever is built for strength not speed, a force can balance a larger resistance when the force arm is longer than the resistance arm
Why does the acceleration of a rocket increase when a constant, sustained force acts on it?
the mass decreases bc less gas
What happens to a skydiver's acceleration between the time they jump from a plane to the time they reach terminal velocity?
the more they speed up, the smaller the acceleration (decreases)
When does a vehicle undergo acceleration?
the object is changing speed or changing direction.
What happens if you apply less force to a horizontally sliding object than is needed to have it maintain a constant velocity?
the object will slow down and eventually come to a complete stop.
A slow pull on the bottom string of a heavy ball hanging by a string breaks which string?
the top one
Which of two people will get to a state of zero acceleration first if a heavy man and a light woman jump from an airplane at the same time and open their same size parachutes at the same time?
the woman bc she is lighter
Why will a feather and a coin have equal accelerations when falling in a vacuum?
there is no air resistance bc the ratio of force to mass is the same
roll
tilt head left or right. (lean head side to side)
moment
torque, rotational force
angular acceleration
torques produce change in angular velocity, vector, change in velocity/ change in time, α alpha
angular distance
total amount of rotation, scalar, Φ Phi
anterioposterior axis
towards front and back of the body, rotation occurs on frontal plane, movements include: adduction, abduction, elevation, depression, lateral flexion, and roll
longitudinal axis
towards top and bottom of the system, rotation occurs along transverse plane, movements include: medial and lateral rotation , yaw
Yaw
turn to left or right (nod no)
couple
two eccentric forces that cause rotation
basic goinometer
used for measuring angles in pictures, static analysis
comparative descriptors
used to describe mechanical characteristics of performance
markers
used to indicate joint center of rotation, and can reflect position of skeletal landmarks
motion capture process
using video or picture cameras to gather images and study a moving system and its parts
total acceleration
vector sum of the tangential acceleration and radial acceleration
tangential velocity
velocity measured at any point tangent to rotating object
Unit for Angular Momentum
w=omega
manipulating inertia
we can manipulate radius of gyration to alter moment of inertia
Pure moment
when 2 forces equal in magnitude but in opposite direction act equidistant from center of gravity, no net force but the 3 forces produce rotation
In what position would a skydiver's terminal velocity be the greatest?
when air resistance equals weight and net force is zero. Headfirst, best chance to accelerate.
rotational movement
when the push or pull influence acts at a point away from an axis of rotation of movement
What is the linear speed of an object given a certain distance from the axis of rotation
(Apply formula on chart)
A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, how much force would be required to keep the puck sliding at constant velocity?
0
Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet?
0
What is a cart's acceleration if it maintains a constant velocity of 100 m/s for 10 s?
0
What is the acceleration of an object that covers a distance of 8 meters in the first second of travel, another 8 meters during the next second, and 8 meters again during the third second?
0
What is the acceleration on an object when it's net force is 0.
0
What is the acceleration on an object when it's net force is 0?
0
What is the speed of a mosquito flying at 3 m/s that encounters a breeze blowing at 3 m/s in the opposite direction?
0 m/s
How quickly will you accelerate away from the wall if you stand on a skateboard and exert a 50-N push and your mass is 60 kg?
0.8 m/s2
Sin (Critical angle) =
1 / Refractive Index
What is the net force of an apple in free fall if at rest it weighs 1 N?
1 N
What is the net force of an apple in free fall if at rest it weighs 1 N?
1 N (free fall neglect air resistance)
What is the mass of a pet turtle that weighs 10 N?
1 kg
What is the acceleration of a cart that changes speed from 90 m/s to 100 m/s in 10 s?
1 m/s/s
What is the acceleration of a 10 kg block that is pushed across a horizontal surface with a force of 20 N against a friction force of 10 N?
1 m/s2
What is the acceleration of a cart that changes speed from 90 m/s to 100 m/s in 10 s?
1 m/s2
When Nellie Newton hangs by the ends of a rope draped over a large pulley, what is the tension in each supporting vertical strand?
1 single rope, each side of the rope would be half of her total weight
What is the vertical height attained by a basketball player that has a hang time of a full 1 s?
1.2 meters
What is the vertical height attained by a basketball player that has a hang time of a full 1s?
1.2 meters
Kinetic Energy =
1/2 x Mass x V^2
How much applied force is needed to maintain the constant velocity of an object sliding against a friction force of 10 N?
10 N
Neglecting air resistance, what is the net force acting on a 1-kg ball that is thrown at 10 m/s straight upward?
10 N
What does a 1-kg mass at the Earth's surface weigh?
10 N
What is the force on the crate if you push with a work of 40 J over a distance of 4 m?
10 N
What does a 1-kg mass at the Earth's surface weigh?
10 N, 2.2 lbs
What is the resulting speed of a motorboat that normally travels at 8 km/h in still water and heads directly across a current moving at 6 km/h?
10 km/h
What is a ball's acceleration when it is thrown straight upwards and reaches the very top if its path?
10 m/s
What is the acceleration of a rock at the top of its path when it is thrown vertically into the air?
10 m/s
What is the acceleration of a ball thrown straight downward (in the absence of air resistance)
10 m/s2
What is the acceleration of a bullet fired straight down from the top of a high cliff if you neglect air resistance?
10 m/s2
What is the acceleration of a rock at the top of its path when it is thrown vertically into the air?
10 m/s2
What is the acceleration of the fall of a rock dropped from a height of 2.5 m if at a 5 m height it accelerated at 10 m/s2 before it struck the ground 1 s later?
10 m/s2
How much force does a 10-kg brick require to accelerate it as compared to a 1-kg brick neglecting friction?
10 times
What is the efficiency of a machine that puts out 100 W of power for every 1000 W it puts in?
10%
What is the rope tension on a rope that is pulled with 100 N of force on one end and 100 N of force on another?
100 N
Where does a boat reach the east bank of a river that is 100 m wide if the water is flowing due south at 1 m/s, the boat is traveling at 1 m/s relative to the water, and it is pointed due east as it crosses from the west bank?
100 farther south
If an airplane travels at 141 km/h toward the northeast, what is its component of velocity due north?
100 km/h
Where does a boat reach the east bank of a river that is 100 m wide if the water is flowing due south at 1 m/s, the boat is traveling at 1 m/s relative to the water, and it is pointed due east as it crosses from the west bank?
100 m further south/downstream
A force of 1000 N is exerted on a ball would have how much force exerted back on it?
1000 N
The force of friction on a sliding object is 12 N. The applied force needed to maintain a constant velocity would have to be what?
12 N, a force equal and opposite
What is the acceleration due to gravity on a planet that requires 1 second to fall a distance of 6 m?
12 m/s2
An object release from rest on another planet requires one second to fall a distance of 6 meters. What is the acceleration due to gravity on this planet? *
12 m/s^2
A pair of 10 N vectors at right angles to each other would have a resultant force of what?
14 N
A pair of 10-N vectors at right angles to each other would have a resultant force of what?
14 N
What is Jake's speed relative to the ground if he runs at 4 m/s along a train flatcar that is moving at 10 m/s in the same direction?
14 m/s
What is the ground speed of an airplane that flies 100 km/h in a 100km/h crosswind?
141 km/h
What is the ground speed of an airplane that flies at 100 km/h in a 100 km/h crosswind?
141 km/h
A tree stump is pulled northward by a 10-N force at the same time a 25-N force pulls it southward. The resultant force has a magnitude of
15 N
A tree stump is pulled northward by a 10-N force at the same time a 25-N force pulls it southward. What is the magnitude of the resultant force?
15 N
What is the support force on a 15 N book at rest on a table?
15 N
What is the support force on a 15-N book at rest on a table?
15 N
When a block is pulled to the left with 20 N and to the right with 5 N at the same time what is the net force at work?
15 N
What is the time it takes a car to attain a speed of 30 m/s when accelerating from rest at 2 m/s/s?
15 seconds
What is the time it takes a car to attain a speed of 30 m/s when accelerating from rest at 2 m/s2?
15 seconds
What is the mass of a car being towed by a tow truck that exerts a 3000 N force on the car if the tow truck is accelerating at 2 m/s2?
1500 kg
What is the depth of a mineshaft if a stone falls to the bottom in 6 seconds.
180 m
What is the depth of a mineshaft if a stone falls to the bottom in 6 seconds?
180 m
How much does a rock weigh on a planet where a 1-kg rock dropped from rest falls 2 m in 1 second?
2 N
How much does a rock w eigh on a planet where a 1-kg rock dropped from rest falls 2 m in 1 second?
2 N weight = mass x gravity
What is the power expended of doing 100 J of work in 50 seconds?
2 W
What is the height of a crate above the ground if it has 40 J of PE and has a mass of 2 kg?
2 m
What is the acceleration of a ball down an incline if it starts from rest at the top and gains a speed of 2 m/s for each second it rolls?
2 m/s/s
What is the acceleration of a 100,000 kg jet that is capable of producing 50,000 N of thrust with each of its 4 engines?
2 m/s2
What is the acceleration of a ball down an incline if it starts from rest at the top and gains a speed of 2 m/s for each second it rolls?
2 m/s2
1 absolute angle
2 markers, one segment and line reference
What is the total time it takes a projectile fired straight up at 10 m/s to reach the top of its path and return to its starting point?
2 s
What is the total time it takes a projectile fired straight up at 10 m/s to reach the top of its path and return to its starting point?
2 seconds
What speed do two freight cars move away at after collision if the 5000 kg car is moving at 2 m/s and the 10,000 kg freight car is at rest?
2/3 m/s
Human Hearing Range
20 - 20,000 Hz
If a hydraulic press has its input piston depressed 20 cm while the output piston is raised 1 cm how much could a 1 N input lift?
20 N
What is the average speed of a horse that gallops 10 km in 30 min?
20 km
What is the average speed of a horse that gallops 10 km in 30 min.?
20 km/h
What distance will you cover if you walk at an average speed of 4 m/s in 5 s?
20 m
What would the speed reading on a speedometer be if a free falling object that was falling on a planet where acceleration due to gravity was 20 m/s/s?
20 m/s
What would the speed reading on a speedometer be if a free falling object that was falling on a planet where acceleration due to gravity was 20 m/s2?
20 m/s
What distance will you cover if you walk at an average speed of 4 m/s in 5/s?
20 meters
What is the ideal output force of a hydraulic jack over a distance of 0.1 m if the input force is 200 N over a distance of 1 m?
2000 N
What is the net force exerted on a 1000-kg car accelerating at 2 m/s2?
2000 N
If an object falls freely from rest on a planet where acceleration due to gravity is twice as much as on Earth, how far would it fall in the first 5 seconds?
250 m
If an object falls freely from rest on a planet where the acceleration due to gravity is twice as much as on Earth, how far would it fall in the first 5 seconds?
250 m
If an astronaut has a mass of 70 kg (weight 700 N) on earth's surface. What would his weight be on the surface of Mars where acceleration due to gravity is 3.7 m/s2?
260 N
What is the ground speed of an aircraft with an airspeed of 200 km/h when it is caught in a 200 km/h crosswind?
283 km/h
How much will you multiply the torque by if you double the length of the effort arm
2x
When a car tows a car with twice the mass of its own, what is its maximum acceleration?
3 Times as big originally, Cuts acceleration 1/3 of what it was before.
What happens as the sloped surface supporting a shoe becomes steeper?
3 forces are affected by this change - the force of friction increases and the slope increases, the overall weight (mxg) remains unchanged, and the support force (N) decreases.
What is a wagon's acceleration if its mass is 10-kg and it is being pulled with a horizontal force of 30 N if no other horizontal forces are at work?
3 m/s2
What is the wagon's acceleration if its mass is 10kg and it is being pulled with a horizontal force of 30 N if no other horizontal forces are at work?
3 m/s2
1 relative angle
3 markers and 2 segments
What speed does a pot hit the ground at if it falls from a ledge and hits the ground 45 m below?
30 km/h
A package falls off a truck that is moving at 30 m/s. Neglecting air resistance, the horizontal speed of the package just before it hits the ground is
30 m/s
A package falls off a truck that is moving at 30 m/s. Neglecting air resistance, what is the horizontal speed of the package just before it hits the ground?
30 m/s
What speed does a pot hit the ground at if it falls from a ledge and hits the ground 45 m below?
30 m/s
What is the speed of a 2000-kg car just before it hits the brakes if it experiences a braking force of 10,000 N and stops in 6 seconds?
30 m/s2
A karate chop breaks a board with a 3000 N blow. What is the amount of force that acts on the hand?
3000 N
What is the friction force between a 300-kg bear and a vertical tree if the bear slides down at a constant velocity?
3000 N
What is the friction force between a 300-kg bear and a vertical tree if the bear slides down at a constant velocity?
3000 N find the bear in newtons then opposite force
A 700-N man stands at rest on two bathroom scales so that his weight is distributed evenly over both scales. What would be the reading on each scale?
350 on each scale
An astronaut on another planet drops a 1 kg rock from rest. The astronaut notices that the rock falls 2 meters straight down in one second. On this planet, how much does the rock weigh? *
4 N
What is the acceleration of a car that starts from rest and 5 seconds later reaches a speed of 20 m/s?
4 m/s/s
What is the acceleration of a car that starts from rest and 5 seconds later reaches a speed of 20 m/s?
4 m/s2
How much work is done when you push an object 2 m using a force of 20 N?
40 J
What is the speed of a heavy object moving upward in the air at 50 m 1 second later?
40 m/s
What is the speed of a heavy object moving upward in the air at 50 m's 1 second later?
40 m/s
Burl and Paul have a total weight of 1500 N. The tensions in the support ropes that support their scaffold add to 1900 N. What must the weight of the scaffold be?
400 N
Burl and Paul have a total weight of 1500 N. The tensions in the supporting ropes that support their scaffold add to 1900 N. What must the weight of the scaffold be?
400 N
How many km/L does a car achieve if it is 20% efficient, encounters a 1000 N resistance force, and the energy content of the fuel is 40 MJ/L?
5 Km
An astronaut on another planet drops a 1 kg rock from rest and finds that it falls a vertical distance of 2.5 meters in one second. On this planet, the rock has a weight of *
5 N
If a mobile phone is pulled by a northward force of 10 N and at the same time is pulled southward by another force of 15 N what is the resultant?
5 N
If a mobile phone is pulled by a northward force of 10 N and at the same time is pulled southward by another force of 15 N what is the resultant?
5 N Southward
What is the resultant speed of a hummingbird that flies at 4 km/h and gets caught in a 3 km/h crosswind?
5 km/h
What will be the speed of a free falling object ½ second after starting from rest?
5 m/s
What will be the speed of a free-falling object 1/2 second after starting from rest?
5 m/s
What is the resultant of a vertical vector of 3 units and a horizontal vector of 4 units?
5 units
What is the speed of a 5 kg fish moving at 1 m/s after swallowing a 1 kg fish at rest?
5/6 m/s= 0.83 m/s
What is the resultant of a 40 N force at right angles to a 30 N force?
50 N
What is the resultant of a 40-N force at right angles to a 30-N force?
50 N
How much power of work is needed to move a toy elevator from the ground floor to the 2nd floor in 20 seconds if the work applied is 1000 J?
50 W
What is the efficiency of a jack system if it can increase the PE of a heavy load by 1000 J with a work input of 2000 J?
50%
If something is attracted to the earth by a 500-N gravitational force, how much is the earth attracted towards it?
500 N
What is that air resistance of on a 500 N skydiver when they reach a terminal velocity of 90 km/h?
500 N
What is the air resistance on a 500 N skydiver when they reach a terminal velocity of 90 km/h?
500 N
What net force would produce the acceleration of 10 g's on a human body with a mass of 50 kg?
500 N
What is the KE of a diver who weighs 500 N diving from a 10 m platform?
5000 J
What net force would produce the acceleration of 10 g's on a human body with a mass of 50 kg?
5000 N
The human body can withstand an acceleration of 10 g's (10 times the force of gravity) under certain conditions. What net force would produce this acceleration for a 50 kg person? *
5000 g
Jason weighs 175 N and sits on his big brother's shoulders. Big brother weighs 410 N. What must the support force be supplied by the floor?
585 N
Jason weights 175 N and sits on his big brother's shoulders. Big brother weights 410 N. What must the support floor be supplied by the floor?
585 N
What is the force of friction between a block and a level surface if the block is dragged without acceleration along a straight-line path across that surface with a force of 6 N?
6 N
What is the force of friction between a block and a surface if it is dragged without acceleration along a straight-line path across a level surface with a force of 6 N?
6 N
What is the net force on a 10 N falling object that that encounters a 4 N air resistance?
6 N or 14 N, depends
What is the net force on a 10 N falling object that encounters a 4 N air resistance?
6 N or 4 N
What is the change in momentum that occurs when a 1.0 kg ball traveling at 4.0 m/s strikes a wall and bounces back at 2.0 m/s?
6 kg m/s
What is a car's speed 3 seconds after accelerating from rest at 2 m/s/s?
6 m/s
What is a car's speed 3 seconds after accelerating from rest at 2 m/s2?
6 m/s
What is the speed of a mosquito that is flying at 3 m/s and encounters a breeze blowing at 3 m/s in the same direction?
6 m/s
What is the acceleration due to gravity on a planet that requires 1 second to fall a distance of 6 m?
6 m/s2
What is the power required to exert a 4-N force over 3 meters in 2 seconds?
6 w
What is the speed of an object 1 s after in free fall is moving downward at 50 m/s?
60 m/s
What is the ground speed of a plane flying at 80-km/h against a 10-km/h headwind?
70 km/h
What is the ground speed of a plane flying at 80km/h against a 10 km/h headwind?
70 km/h
What is the GPE of a 2-kg ball held 4 m above the ground, relative to the ground?
80 J
How far will a motorcycle skid with locked brakes at 150 km/h compared to a motorcycle moving at 50 km/h skidding 10 m?
90 m
How do you define impulse?
A change in an object's momentum.
What is an example of an object that has a center of mass where no exists
A hollow ball Any type of ball that is inflated with air.
Is it possible to have a machine that promises more energy output than input?
A machine cannot produce more energy output than it has input. NO
What is torque?
A turning force
Suppose you are swirling a can around and suddenly decide to pull the rope in halfway; by what factor would the speed of the can change? A. Double B. Four times C. Half D. One-quarter
A. Double Angular Momentum is proportional to radius of the turn. No external torque acts with inward pull, so angular momentum is conserved. Half radius means speed doubles. Angular momentum = mass tangential speed x radius
Suppose you take a sharper turn than before and halve the radius, by what factor will the centripetal force need to change to prevent skidding? A. Double B. Four times C. Half D. One-quarter
A. Double Because the term for "radius" is in the denominator, if you halve the radius, the centripetal force will double.
Suppose by pulling the weights inward, the rotational inertia of the man reduces to half its value. By what factor would his angular velocity change? A. Double B. Three times C. Half D. One-quarter
A. Double Angular momentum is proportional to "rotational inertia." If you halve the rotational inertia, to keep the angular momentum constant, the angular velocity would double. Angular momentum = rotational inertia x angular velocity
Loudspeaker
A.C electrical signals - from amplifier - to coil of wire - wrapped around cone Cone surrounded - permanent magnet - cause a force forwards + backwards Movements = cone vibrate = sound
Absolute 0 - Kelvin Scale
Absolute 0 - atoms have as little kinetic energy as possible Absolute 0 = -273°C 50 Kelvin = -223°C 15°C = 288 Kelvin
A free-falling watermelon falls with a constant what?
Acceleration
If you double the net force on an object what also doubles?
Acceleration
How much force does a 10-kg brick require to accelerate it as compared to a 1-kg brick if you neglect friction?
Acceleration is directly proportional to net force, therefore 10 times as much force would be required to move an object with 10 times the mass as something else.
A free-falling watermelon falls with a constant what?
Acceleration stays constant
What happens to the acceleration of an object that experiences a tripling of its net force?
Acceleration triples
How should a mosquito hover you to join you for lunch if a mild 2 m/s breeze is blowing?
Against at 2 m/s and opposite the speed of a breeze.
How should a mosquito hover over you to join you for lunch if a mild 2 m/s breeze is blowing?
Against the breeze 2 m/s
The earliest and most influential Greek philosopher was Aristotle. What are some of his teachings?
All motion is either natural or violent, there are four elements in nature- earth, fire, water, and air, any type of violent motion requires an external force
The earliest and most influential Greek philosopher was Aristotle. What were some of his teachings?
All motion is either natural or violent; there are four elements in nature - earth, water, air, and fire; any type of violent motion requires a sustained push or pull
A red car has a head-on collision with an approaching blue car with the same magnitude of momentum. A green car driving with the same momentum as the other cars collides with an enormously massive wall. Which of the three cars will experience the greatest impulse?
All the same impulse
Wave Info
All waves transfer energy and information without transferring matter
Marsden experiment
Alpha particles were detected as tiny flashes of light on screen Most alpha particles went straight thought gold foil A small number deviated as they were repelled Very few alpha particles bounced back because of the dense nucleus
Centrifugal Force
Although centripetal force is center directed, an occupant inside a rotating system seems to experience an outward force. This apparent outward force is called centrifugal force. Centrifugal means "center-fleeing" or "away from the center."
About which axis would the rotational inertia of a pencil be the greatest
An axis about its end
What needs to exist in order to produce an acceleration to a system?
An external force must be applied to a system in order for the system to accelerate.
What force accelerates the orange and apple system that we looked at in our notes?
An external force that is outside the system - the friction from the floor
Angular Momentum, Continued-1
An external net torque is required to change the angular momentum of an object. Rotational version of Newton's first law: An object or system of objects will maintain its angular momentum unless acted upon by an external net torque.
What is rotational inertia?
An object at rest remains at rest and an object that is rotating remains rotating unless acted upon by an outside torque
What describes an object in mechanical equilibrium?
An object in mechanical (static) equilibrium is not moving and net force is 0
What describes an object in mechanical equilibrium?
An object in mechanical (static) equilibrium is not moving and the net force on it is zero.
Rotational Inertia
An object rotating about an axis tends to remain rotating about the same axis at the same rotational speed unless interfered with by some external influence. The property of an object to resist changes in its rotational state of motion is called rotational inertia (symbol I).
Two people, one twice as massive as the other, attempt a tug of war with 12 meters of rope on frictionless ice. After a brief time they meet. The heavier person slides what distance?
An object that is twice as massive will slide half as far.
For every action force there must be what?
An opposed reaction
Total internal reflection - Optical fibres
Angle of Incident is always higher than critical angle, light always totally internally reflected - only stops if fibre is to sharp
What do you get when you multiply linear momentum x radial distance
Angular momentum (when multiplied by radial distance you get angular momentum) "M*V*R"
Of a given series of animal determine which has the quickest stride
Animals with shorter legs will have quicker strides.
Centripetal Force
Any force directed toward a fixed center is called a centripetal force. Centripetal means "center-seeking" or "toward the center." Example: To whirl a tin can at the end of a string, you pull the string toward the center and exert a centripetal force to keep the can moving in a circle.
What are examples of vector quantities?
Any quantity with both magnitude and direction is a vector quantity, such as velocity or forces.
What are examples of vector quantities?
Any quantity with magnitude and direction, velocity or forces
What does the equilibrium rule F=0 apply to?
Applies to both objects at rest and objects in motion at a constant rate
What does the equilibrium rule apply to?
Applies to objects at rest (static/mechanical equilibrium) and object in motion at a constant rate (dynamic equilibrium
What increases when an iron block near the earth's surface is in free fall?
As an object falls its speed increases due to the acceleration due to gravity that it experiences.
Why does the acceleration of a rocket increase when a constant, sustained force acts on it?
As the rocket travels upward it is burning large amounts of fuel by the second causing its mass to become less and less every second.
What direction would result from a combined wreck of two vehicles with equal magnitudes of momentum traveling at right angles to each other? (This is an inelastic collision)
At a 45 degree angle to the direction of the cars before the collision
What is the minimum number of forces that act on a book resting on a table?
At least two
When does a ball rolling down an inclined plane have its maximum PE?
At the top of the inclined plane.
If a sledge hammer is held vertically which way is it easier to balance
At the top, away from the handle.
When does a ball rolling down an incline have its maximum KE?
At the very bottom of the incline.
A hoop and a disk are released from the top of an incline at the same time. Which one will reach the bottom first? A. Hoop B. Disk C. Both together D. Not enough information
B. Disk Explanation: Hoop has larger rotational inertia, so it will be slower in gaining speed.
Suppose you double the speed at which you round a bend in the curve, by what factor must the centripetal force change to prevent you from skidding? A. Double B. Four times C. Half D. One-quarter
B. Four times Because the term for "tangential speed" is squared, if you double the tangential speed, the centripetal force will be double squared, which is four times.
Why does a heavier person sit closer to the fulcrum on a seesaw than a lighter person?
Because both people have the same torque
If the track has a small upward dent, how does the time it takes to roll the length of the track compare to a track with no dent?
Because the ball has to roll up the small hill and back down the small hill, the time it takes to do so will be greater than if there was no small dent in track at all
Why is the speed of a cannon's recoil relatively small compared to the speed of the cannonball?
Because the cannon has a greater mass.
Why is a meter stick balanced in the center?
Because the torque is zero since there is no lever arm
Two identical arrows, one with twice the KE of the other, are fired into a bale of hay. Compared with the penetration of the slow arrow, how far would the faster arrow penetrate?
Begin with W = F x d, W = Δ KE. 2 times the amount of KE would produce how much greater of a distance? Four times as much.
If you toss a coin straight upward in a train that gains speed while the coin is in the air, where will the coin land?
Behind you
To spin a football where do you apply force?
Below or above the CM
Which undergoes a greater change in momentum, a bug that splatters onto your windshield while you are driving down the highway or the windshield as it smashes the bug?
Both are the same - Conservation of Momentum
How does pushing a shopping cart twice as far with twice the force impact the amount of work you do?
By doubling both the amount of F and the d you do 4 times the amount of work.
A ladybug sits halfway between the rotational axis and the outer edge of the turntable. When the turntable has a rotational speed of 20 RPM and the bug has a tangential speed of 2 cm/s, what will be the rotational and tangential speeds of her friend who sits at the outer edge? A. 1 cm/s B. 2 cm/s C. 4 cm/s D. 8 cm/s
C. 4 cm/s Explanation: Tangential speed = rω Rotational speed of both bugs is the same, so if radial distance doubles, tangential speed also doubles. 2 cm/s x 2 = 4 cm/s So, tangential speed is
What is the momentum of a 100 kg motorcycle that rolls of the edge of a cliff and falls for 3 s before hitting the bottom of a gully?
Calculate the weight of the motorcycle due to gravity. Then multiply the weight of the motorcycle by the amount of time gravity acts. m=100 t=3s w= 1000N (100kgx10m/s) then 1000N x 3s= 3000 kg m/s
When a cannonball is fired from a cannon, which undergoes a greater acceleration, the cannon ball or the cannon?
Cannonball
Dangers of Gamma
Cell mutation and Tissue damage - can cause cancer
Center of Mass and Center of Gravity
Center of mass is the average position of all the mass that makes up the object. Center of gravity (CG) is the average position of weight distribution. Since weight and mass are proportional, center of gravity and center of mass usually refer to the same point of an object.
Simulated Gravity
Centrifugal force can be used to simulate gravity in space stations of the future. By spinning the space station, occupants would experience a centrifugal force (simulated gravity) similar to the bug in the can.
Rotating Reference Frames
Centrifugal force in a rotating reference frame is a force in its own right - as real as any other force, e.g. gravity. Example: The bug at the bottom of the can experiences a pull toward the bottom of the can.
Acceleration =
Change in Velocity / Time Taken
Thermistor Explanation
Changes in resistance as temperature changes In hot condition the resistance decreases In cool conditions the resistance increases Acts as temperature detectors
LDR Explanation
Changes it resistance depending on the amount of light In bright light the resistance decreases In dark light the resistance increases Acts as a light sensor
Effects of gravity on planets
Closer you get to a star or a planet the stronger the force of attraction is, so they move quicker in orbit
Which experiences a greater air resistance - a bird's feather falling from a tree to the ground or a coconut doing the same?
Coconut
How far will a bicycle skid if its speed is reduced to half before skidding to a stop?
Compare the skidding distance to the amount that KE changes if the speed is reduced to half. 1/4 as much.
What happens when a rocket ship gaining speed in outer space runs out of fuel?
Continue moving at the rate of speed it was going when it ran out of fuel
Which has greater momentum when moving: a container ship or a bullet?
Could be either one depending on the velocity of each
Parallel Circuit
Current = Current of all components Voltage the same
Series Circuit
Current the same Voltage = Voltage of all components
Suppose the girl on the left suddenly is handed a bag of apples weighing 50 N. Where should she sit order to balance, assuming the boy does not move? A. 1 m from pivot B. 1.5 m from pivot C. 2 m from pivot D. 2.5 m from pivot
D. 2.5 m from pivot Explanation: She should exert same torque as before. See powerpoint for example with formula
Dangers of Ultraviolet
Damage surface cells and causes blindness
What happens to a skydiver's acceleration as their velocity of fall increases?
Decreases
What happens to the speed of a freight car rolling friction free along a horizontal track in pouring rain as water accumulates inside of the car? (the rain is falling vertically)
Decreases
What is Katelyn's speed relative to an observer at rest on the ground if Katelyn runs along the aisle of a train moving at 8 m/s and her speed relative to the floor is 3 m/s?
Depends on direction
Rotational Inertia, Continued
Depends upon mass of object. distribution of mass around axis of rotation. The greater the distance between an object's mass concentration and the axis, the greater the rotational inertia.
Centripetal Force, Continued
Depends upon mass of object. tangential speed of the object. radius of the circle. In equation form: Centripetal force = mass x tangential speed^2/radius
Rotational Inertia, Continued-2
Depends upon the axis around which it rotates Easier to rotate pencil around an axis passing through it. Harder to rotate it around vertical axis passing through center. Hardest to rotate it around vertical axis passing through the end.
What is the relationship in acceleration if two bullets fall into a river from a very high bridge if one is dropped from the bridge and the other is fired from it?
Despite one being fired and the other dropped, they will both accelerate at the same rate. Their speeds will be different from each other at any given point, but not their rate of acceleration.
If you toss a coin straight upward while in a train moving at constant velocity, the coin will land
Directly below where you tossed it originally
What are the two necessary measurements for calculating speed?
Distance the object traveled and amount the time it has taken to travel that distance
Voltage
Driving force which pushes current (Electrical Power)
A hockey puck sliding at constant velocity across the ice is considered to be in what?
Dynamic equilibrium
A hockey puck sliding at constant velocity across the ice is considered to be in what?
Dynamic equilibrium- it is in motion at constant rate
If Nellie hangs from a horizontal bar that is supported by four vertical ropes, the tension in the ropes
Each rope would support 1/4 her weight, add to equal her weight
If Nellie hangs from a horizontal bar that is supported by four vertical ropes, what is the tension in the ropes?
Each rope would support ¼ of her weight
An 700-N man stands at rest on two bathroom scales so that his weight is distributed evenly over both scales. What would be the reading on each scale?
Each scale should show half of his weight
What does your weight displayed on your bathroom scale measure?
Earth's gravity pull on you
What is Katelyn's speed relative to an observer at rest on the ground if Katelyn runs along the aisle of a train moving at 8 m/s and her speed relative to the floor is 3 m/s?
Either depending on her running direction
Examples of Transverse Waves
Electromagnetic Waves Ripple in Water
In what two ways do action and reaction forces always act?
Equal and opposite
How much force does the Earth pull on the moon with?
Equal and opposite force
What is the impact force of an automobile and a golf cart that collide head-on after traveling at the same speed?
Equal and opposite. The car can only apply as much force as the golf art applies back against it.
How would the speed reading increase if a free falling object were equipped with a speedometer?
Every second an object falls, increases by 10 m/s
What is the acceleration of the fall of a rock dropped from a height of 2.5 m if a 5 m height it accelerated at 10m/s/s before it struck the ground 1 s later?
Everything accelerates the same at earth
What would happen to the rate of rotation about the axis of a planet if the planet underwent a gravitational collapse
Everything would be pulled inward and collapse so it will rotate faster and increase
A moving van with a stone lightly glued to the midpoint of its ceiling smoothly moves at constant velocity. When the glue gives way, the stone falls and hits the floor?
Exactly below the point it was glued on the ceiling
A moving van with a stone lightly glued to the midpoint of its ceiling smoothly moves at constant velocity. When the glue gives way, where does the stone fall and hit the floor?
Exactly below the point it was glued on the ceiling.
Conservation of Angular Momentum, Continued
Example: When the man pulls the weights inward, his rotational speed increases!
What force exerted on the rocket causes the rocket to accelerate into space?
Exhaust gases that are leaving the rocket.
If you can't avoid being hit by a fast-moving object, how you can you suffer a smaller contact force?
Extend the amount of force over a long amount of time.
Hookes Law
Extension is directly proportional to force until the spring reaches it's elastic limit
Determine the mass of a meter stick if it has a mass suspended from it a certain distance away from its center of gravity
F*D of both sides.... F*D=F*D
Angular Momentum, Continued
For an object that is small compared with the radial distance to its axis, magnitude of Angular momentum = mass tangential speed x radius This is analogous to magnitude of Linear momentum = mass x speed Examples: Whirling ball at the end of a long string Planet going around the Sun
What does a newton measure?
Force
Pressure =
Force / Area
Work involves what two factors?
Force and distance.
Gravity
Force of attraction between all masses
Work Done =
Force x Distance Moved
Moment =
Force x Perpendicular Distance from Pivot
What does a newton measure?
Force, weight
Wave Speed =
Frequency x Wavelength
Why does a hockey puck sliding across the ice finally come to rest?
Friction
From what frame of reference would centrifugal force be an apparent reality for a rotating object
From within the rotating object For the person in the system who is observing it.
Solar Systems
Galaxy = large collection of stars Sun = one of many stars
Who was the first scientist to introduce the concept of Inertia?
Galileo
Who was the first scientist to introduce the concept of inertia?
Galileo
A ball rolls along a horizontal track in a certain time. If the track has a small upward dent, how does the time it takes to roll the length of the track compare to a track with no dent?
Greater
What is the magnitude of the combined wreck of two vehicles with equal magnitudes of momentum traveling at right angles to each other after undergoing an inelastic collision?
Greater than their individual momentums
If you suspend your body from a pair of vertical ropes what will the tension in each rope be?
Half of your body weight if evenly from each
When does a block of ice sliding down an inclined plane have half of its maximum KE?
Halfway down the incline.
How would the hang time on Earth be compared to that on the Moon?
Hang time on Moon is greater
How would the hang time on Earth be compared to that on the moon?
Hang time on the Moon would be greater because the effect of gravity is less
Artificial Earth Satellites
Have orbital period of 1 day = geostationary satellites, used for communications
In what orientation would a skydiver's terminal velocity be the greatest?
Head first
Pressure Difference =
Height x Density x Gravity
What would be the ideal KE of an arrow that is fired if the bow is drawn to a PE of 40 J?
Ideal KE is equal to the amount of PE when the bow is drawn.
What would happen to your weight if Earth rotated more slowly about its axis
If earth rotates slower your weight increases. This is because when the earth is moving slower it takes more force to keep you on the earth.
Calculate the relationship between a change in gravity's impact in one's ability to jump. If you can jump 1m with 1 g of gravity.
If gravity is lessened by ¼ you will be able to jump 4 x as much
When Nellie Newton hangs by the ends of a rope draped over a large pulley, what is the tension in each supporting vertical strand?
If it is 1 single rope, each side of the rope would be half of her total weight
The force of friction on a sliding object is 12 N. The applied force needed to maintain a constant velocity would have to be what?
If object is moving, force equal and opposite to the force of friction, if object isn't moving, slightly greater force
How much work do you do when you push a shopping cart twice as far while applying the same force?
If the amount of force remains the same, but the distance you have to push doubles, the amount of work you must do doubles.
What is the minimum number of forces that act on a book resting on a table?
If the book is at rest there must be at least two.
When would more braking force be required on a car if it is traveling along the highway and brakes to a stop over a certain distance?
If the car had more mass, if it had less distance to stop in, or if it had more momentum.
Someone's weight and normal force usually have the same magnitude when they are standing on a surface going which direction to them?
If the surface is perpendicular (horizontal) to them.
How is the amount of PE affected when you lift a crate that gains 200 J of PE 10 m compared to lifting it 20 m high?
If you double the height the object is being lifted, you double the amount of PE it has.
What characterizes the KE of an object?
In order for an object to have KE it has to be moving.
Why is pike position more gaining than a tuck position?
In pike position there is more rotational inertia which makes it harder to change position
What did Galileo teach us about rolling a ball along a level surface?
In the absence of any outside force acting on the ball, it will continue to roll forever in the direction it was pushed
What did Galileo teach us about rolling a ball along a level surface?
In the absence of any outside force acting on the ball, it will continue to roll forever in the direction it was pushed.
Two identical freight cars roll without friction (one at 1 m/s, the other at 2 m/s) toward each other on a level track. They collide, couple together, and roll away in what direction?
In the direction of the one with the greater speed.
How is the amount of power you expend on a skateboard impacted by cutting the time it takes you to do the work by ⅓?
In the equation P = W / t, if you cut the amount of time by ⅓ you triple the amount of power output you have.
What would happen to the spin of the earth if all people, animals, trains, trucks, etc. all began to walk or run towards the east? (opposite of earth's spin)
In theory, Earth would spin slightly slower.
Why do you hold out your arms when walking along a fence?
Increase rot in
Circuit Rules
Increase voltage = more current will flow Increase resistance = less current will flow
What is the distance a free falling bowling ball falls each second?
Increases 10 m/s
What is the distance a free-falling bowling ball falls each second?
Increasing each second at predictable rate
An object with twice as much mass as another object has twice as much what to overcome?
Inertia
If your automobile runs out of fuel while driving, the engine stops. Why don't you come to an abrupt stop?
Inertia
Why can a sheet of paper can be quickly jerked beneath a container of milk without toppling?
Inertia
What will happen to a ball when you quickly jerk a cart forward that has the ball resting in the middle?
Inertia will cause the ball to remain where it was before the cart moved, so it hits the back
While you are standing in the aisle of a bus, the driver suddenly makes a left turn. Why do you lurch to the right?
Inertia, your tendency to keep moving forward.
What measurement does the speedometer of an automobile read?
Instantaneous Speed
What does the long, heavy tail of a spider monkey enable the monkey to vary
It allows the monkey to alter its angular momentum Allow it to adjust it's center of gravity to maintain its stability as it moves through the trees.
Where is the center of mass located on a human body
It changes as the person bends over. Typically tends towards the middle of the body. Belly Button but it can change
Why is force a vector quantity?
It has magnitude and direction
How does the increase in speed of an habitat rotating in space affect the weight experienced by the occupants
It increases the weight experienced by the occupants
Centrifugal Force - A Common Misconception
It is a common misconception that a centrifugal force pulls outward on an object. Example: If the string breaks, the object doesn't move radially outward. It continues along its tangent straight-line path—because no force acts on it. (Newton's first law)
Why is it difficult to accelerate a car on a level surface on the moon?
It is difficult because the mass of the car has not changed. Mass is independent of gravity. Weight is determined by the force of gravity.
What does a torque acting on an object produce
It produces rotation
If you double the diameter of a flywheel how does that impact its change in rotational inertia
It quadruples (4x) the rotational inertia of the object
As you toss pizza dough up into the air what happens to its rotational speed as the dough widens out
It slows down
If no external forces act on a moving object, how will it behave?
It will continue to move at the rate it is going
If no external forces act on a moving object, how will it behave?
It will continue to move at the rate it is going.
What does a car tend to do if you release the brakes after slowing from 60 km/h to 40 km/h on the highway?
It will continue to move at the speed that you slowed down to unless another force causes it to do otherwise.
Weigh yourself on a weighing scale and the scale shows your normal weight. What will the scale read if you stand on your tiptoes?
It will read the same
Weight yourself on a weighing scale and the scale shows your normal weight. What will the scale read if you stand on your tiptoes?
It will read the same
Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the tendency of the rock is to
It will travel in a straight line from the point at which the string broke
A roller-coaster ride with 6 passengers takes 3 minutes. Neglecting friction, how long would a similar ride with 12 passengers aboard take?
It would take the same amount of time.
Why does the famous Leaning Tower of Pisa not fall over
Its center of gravity falls within its base
If an object on a rotating body is moved to a point twice as far from the center what happens to its linear speed
Its linear speed will double
What is the acceleration of a ball thrown straight downward?
Its speed might change as it falls but its rate of change in speed, acceleration, will remain constant. 10 m/s/s
What is a ball's acceleration when it is thrown straight upwards and reaches the very top of its path?
Its speed would be zero, but its acceleration remains constant
Law of Conservation of Angular Momentum
Iwtotal=Iwtotal
To produce a large torque do you need a small or large lever arm?
Large
A bird sitting on the limb of a tree is moving about 30 km/s with respect to the Sun. If the bird takes 1 second to drop down to a worm below, the worm would be 30 km downrange from the bird when it reached the ground. This faulty reasoning is best countered with Newton's laws?
Law of inertia
Which concept is being illustrated when a tablecloth is quickly yanked beneath dishes resting on a table?
Law of inertia
Which tennis ball will hit the ground first if 2 are dropped from a tall building and one of them is filled with lead pellets?
Lead pellets
Nellie hangs from a pair of ropes at an angle. Tension in the ropes depends on the?
Length of each rope and the angle the ropes are set at
What is the speed of a ball because of air resistance when it is thrown vertically into the air and returns to the same starting level?
Less, slower than before
Give an example of two of the same tasks, one of which requires more work.
Lifting two objects of the same mass but in one scenario you lift the object twice as high.
Which of two people will get to a state of zero acceleration first if a heavy man and a light woman jump from an airplane at the same time and open their same size parachutes at the same time?
Light Woman
What is the difference between linear momentum and angular momentum
Linear momentum is mass times velocity with angular momentum is mass times velocity times the radius The types of speed and the radial distance.
Density =
Mass / Volume
What does rotational inertia depend upon?
Mass and locating of mass
Be able to determine which object has a greater mass based on clues.
Mass is based on concentration of matter.
Force =
Mass x Acceleration
Weight =
Mass x Gravity
GPE Potential Energy =
Mass x Gravity x Height
Resistance of LDRs and Thermistors Experiments
Measure current at any know/fixed temp Measure voltage at any known/fixed temp Vary temp and take new readings Calculate and draw voltage - current graph Repete and average
Types of orbit
Moons and planets have slightly elliptical orbits Comets orbit the sun, they have very elliptical orbits
Conclusion of Marsdens experiment
Most of atom is empty space Nucleus is small Nucleus is dense Nucleus is positive
Where could you move to if you lived in the Northern Hemisphere and you wanted to weigh less
Move further away from the center of the Earth - towards the Equator.
What is the speed of a ball because of air resistance when it is thrown vertically into the air and returns to the same starting level?
Moving slightly slower than before when it returns.
If a large person and a small person both pull on opposite ends of a rope in a competition of tug of war, the greater force on the rope is exerted by who?
Neither, they are the same
Two students engaged in a tug-of-war each pull a rope in opposite directions with a force of 300 N. The net force on the rope is
Net force is 0
Two students engaged in a tug-of-war each pull a rope in opposite directions with a force of 300 N.What is the net force on the rope?
Net force is 0
What is the net force acting on an insect falling downward at a constant velocity?
Net force is 0
What is the net force of an insect falling downward at a constant velocity?
Net force is 0
What is measured at zero if a car travels around a circular track at a constant speed?
Net force is 0, acceleration and velocity are not because it is constantly changing direction
Nellie pulls with a force of 30 N on a horizontal rope tied to a tree at rest. What is the net force on the rope and the tension force on the rope?
Net force is 0, the tension force is 30 N
Nellie pulls with a force 30 N on a horizontal rope tied to a tree at rest. What is the net force on the rope and the tension force on the rope?
Net force of 0, 30 N
What is the unit for torque
Newton Meters
The impulse-momentum relationship is a direct result of which of Newton's Laws?
Newton's 2nd Law - Law of Acceleration
The Law of Conservation of Momentum is most closely related to which of Newton's Laws?
Newton's 3rd Law - Action/Reaction
In what units does one properly express the weight of an object in physics?
Newtons
What forces are at work on a ball once it leaves your hand, neglecting air resistance?
Nothing but gravity
What kind of adjustments would a gymnast performing somersaults in a high-flying plane moving at constant velocity need to make?
Nothing different
How would the speed reading increase if a free-falling object were equipped with a speedometer?
On earth an object accelerates at a rate of 10 m/s2 which means that every second an object falls its speed increases by 10 m/s.
Power
One Watt = 1 joule of energy transferred per second
Which jar will run down an incline in the shortest time - a filled one or an empty one
One that is full. An empty one has all the weight on the outside rim causing slower rotation.
What speed does a free-falling cantaloupe have 12 s after starting from rest?
Over 100 km
What is the velocity of a 4 kg ball with a momentum of 12 kg*m/s?
P = m x v (Rearrange equation to solve for v) 3 m/s
What is the mass of a ball moving at 3 m/s with a momentum of 48 kg*m/s?
P = m x v (rearrange equation to solve for m)= 16 kg
What is the average braking force needed for a 1000 kg car moving at 10 m/s stopping in 5 s?
P = m x v; F = P/t 2000 N
Convection
Particles from their hotter region to the cooler region and take their heat energy with them
Measuring speed of sound
Person at one end with a pistol Other person at a distance a way from the pistol (e.g 500 metres) Person fires gun People with stopwatches start time when see the smoke from gun and stop when they hear the bang Average the time
Refraction of light experiment
Place block on sheet of paper Draw around the block Turn ray box on and shine beam of light into block use pencil to mark path of light into and out of block Remove the block, measure the angle of refraction Repeat
Investigating the magnetic field experiment
Place sheet of paper on wooded bench (avoid interaction with other magnets) Place magnet on sheet of paper Place plotting compass against the magnet Mark position of compass needle on the paper with a dot Move plotting compass so that the tail of the arrow sits where the tip of the arrow was Repeat process Join dots
Conduction
Process where vibrating particles pass on their kinetic energy
Uses of Waves
Radio Waves: Communication Microwaves: Satellite Communication Infra-Red Radiation: Heating and monitor temperature Visible Light: Travel though optical fibres + Photography Ultraviolet Light: Fluorescent Lamps X-Rays: See inside things Gamma Rays: Sterilising medical equipment
Current
Rate of flow of Charge
What distance per liter can be achieved on the highway with a 100% efficient engine burning a fuel that has a 40 MJ/L energy content that has total forces at work of 1000N?
Rearrange W = F x d formula to solve for d. Remember to first convert 40 MJ to J.= 40Km
What is the acceleration of a bullet fired straight down from the top of a high cliff if you neglect air resistance?
Regardless of the initial velocity it is given cannot accelerate any more than the rate at which gravity can accelerate it. 10 m/s
Recognize vector and non-vector quantities.
Remember that vector quantities contain both magnitude and a direction. Speed for example is a scalar quantity because it can only measure magnitude.
What is the resultant of a pair of equal-length, right angle vectors, if the angle between the vectors is greater than 90 degrees?
Resultant is greater
When Burl and Paul stand on opposite ends of a sign-painting scaffold, what are the tensions in the supporting ropes?
Rope tension on each side depends upon how much each of them weigh.
When Burl and Paul stand on opposite ends of a sign-painting scaffold, the tensions in the supporting ropes
Rope tension on each side depends upon how much they weigh
Circular Motion—Rotational Speed
Rotational (angular) speed is the number of rotations or revolutions per unit of time (symbol ω). All parts of a rigid merry-go-round or turntable turn about the axis of rotation in the same amount of time. So, all parts have the same rotational speed. Tangential speed =Radial Distance x Rotating speed V = r w
What is angular momentum?
Rotational inertia x rotational velocity
A roller-coaster ride with 6 passengers takes 3 minutes. Neglecting friction, how long would a similar ride with 12 passengers aboard take?
Same amount of time
What is the force of impact of a car traveling at 100 km/h striking a bug and splattering it?
Same for both
How does a Newton's cradle device relate to the Law of Conservation of Energy?
Shows that E cannot be created or destroyed. Transferred from one object to another.
Refractive Index =
Sin (I) / Sin (R)
What would the maximum acceleration of a car be if it tows a 2nd car of the same mass?
Since the car's mass doubles due to the additional mass, its acceleration is cut in half.
Dangers of Infra-Red
Skin Burns - Heating effect
How is inertia defined?
Sluggishness, either object's tendency to remain at rest unless non-zero force acts on it or object's tendency to remain in motion unless a non-zero force acts on it
How is inertia defined?
Sluggishness. Either an object's tendency to remain at rest unless an non-zero force acts on it or an object's tendency to remain in motion unless a non-zero force acts on it.
Brownian Motion
Small particles have a constant, rapid and random movement - small particles can move larger particles - causes pressure This discovery was proved with the use of pollen grains
Why does a solid disk reach the bottom of an inclined plane rather than a hollow disk?
Solid disk has less rotational inertia so it is easy to change motion
Resistance
Something which slows down the flow
Examples of Longitudinal Waves
Sound + Ultrasound Shock Waves
Why might a wine glass not break when it falls onto a carpeted floor compared to falling on a stone floor?
Stopping time is longer when the object hits a carpeted surface.
If gravity between the Sun and Earth suddenly vanished, Earth would continue moving in
Straight line from the point at which gravity vanished
What does tension force have the tendency to do?
Tendency to act equal and opposite to the objects causing the tensions
What does tension force have the tendency to do?
Tension force has a tendency to act equal and opposite to the object(s) causing the tension.
If you suspend your body from a pair of vertical ropes what will the tension in each rope be?
Tension in each rope will be half of your body weight if you are suspended evenly from each.
When a car tows a car with twice the mass of its own, what is its maximum acceleration?
That cuts its acceleration to ⅓ of what it was before.
Angular Momentum
The "inertia of rotation" of rotating objects is called angular momentum. This is analogous to "inertia of motion", which was momentum. Angular momentum = rotational inertia x angular velocity This is analogous to Linear momentum = mass x velocity
What happens to a skydiver's acceleration between the time they jump from a plane to the time they reach terminal velocity?
The acceleration of the skydiver becomes less and less as they get closer to terminal velocity.
What do you know about the PE & KE energy of a circus diver half way down, who drops from a high pole into the water far below?
The amount of KE and PE that it has are equal.
When a marble has rolled halfway down an incline what do you know about its KE?
The amount of KE and PE that it has are equal.
Compared to dropping a ball from a high ladder that strikes the ground with 100 J of KE, what would be the KE of a ball thrown into the air and soon reaches the ground? (Neglect air resistance)
The amount of KE is the same.
If a bicycle is traveling 4x as fast as another, what will be its skidding distance when it brakes to a stop?
The amount of KE the bike has is equal to how far it skids. 16 times as much.
Two identical arrows, one with twice the speed of the other are fired into a bale of hay. Compared with the penetration of the slow arrow, the faster arrow penetrates how far?
The amount the arrow penetrates the bale of hay is equal to the amount of KE it has if it is going twice as fast as the other. Four times as far.
What is the reaction force if an archer shoots an arrow if the action force is the bowstring against the arrow?
The arrow against the bowstring.
What is true of the momentum of a baby carriage in comparison to a large heavy truck if both roll down a hill, neglecting friction?
The baby carriage has less momentum because it has less mass.
What is the force exerted on a ball when you drop it on the floor and it bounces back?
The ball pushes on the floor, the floor pushes back with an equal and opposite force.
What are the action/reaction forces involved in the force of lift experienced by a helicopter?
The blades of the rotors push on the air and the air pushes back.
How is the strength of a boxer's punch dependent upon a punching bag?
The boxer can only apply as much force to the punching bag as the punching bag can provide back.
How does the KE of a recoiling cannon compare to a fired cannonball?
The cannonball has a larger amount of KE because it is moving faster.
If your automobile runs out of fuel while you are driving, the engine stops but you do not come to an abrupt. How?
The car has a certain amount of inertia that it had prior to running out of gas, continue to move until friction and air resistance bring it to a stop
If you toss a coin straight upward in train that gains speed while the coin is in the air, the coin will land?
The coin will land behind you
If you toss a coin straight upward while in a train moving at constant velocity, where will the coin land?
The coin will land directly below where it was tossed originally.
If you toss a coin straight upward in train that slows while the coin is in the air, where will the coin land?
The coin will land in front
If you toss a coin straight upward in a train that slows while the coin is in the air, where will the coin land?
The coin would land in front of you.
If a firecracker bursts while free falling what would be true about the combined momentum of its fragments?
The combined momentum is equal to the amount of momentum the fireworks had before the burst.
Define lever arm
The distance between the fulcrum and the force
If a bicycle is traveling twice as fast as another, how far will it skid when braking to a stop?
The distance of the skid is equal to the amount of change in KE.
What happens as water drops fall at a steady rate from a leaky faucet?
The droplets get further apart as they move away from the faucet because their speed changes incrementally as they accelerate towards the ground.
Torque, Continued
The equation for Torque is Torque = lever arm x force The lever arm depends upon where the force is applied. the direction in which it acts.
What does the equilibrium rule, ΣF = 0 apply to?
The equilibrium rule applies to both objects at rest and objects in motion at a constant rate.
What does the equilibrium rule apply to?
The equilibrium rule applies to objects at rest (static/mechanical equilibrium) and objects in motion at a constant rate (dynamic equilibrium).
How does the speed of an object depend on its distance away from the axis of rotation
The farther away from the axis of rotation an object is the greater its speed. The object's speed is higher if the object is closer to the axis of rotation, lower if it is further away.
A bird sitting on the limb of a tree is moving about 30 km/s with respect to the Sun. If the bird takes 1 second to drop down to a worm below, the worm would be 30 km downrange from the bird when it reached the ground. This faulty reasoning is best countered with which of Newton's laws?
The first law - the law of inertia
When you walk, you push on the floor. What does the floor do to you?
The floor pushes back with an equal and opposite force.
Where does the force come from that is exerted on the tires of a car that directly accelerates it along a road?
The force comes from the road (friction against the tires).
What do you know about the force that propels a cannonball when fired from a cannon?
The force is equal and opposite to the force that acts on the cannon to cause it to recoil. The acceleration of the cannonball compared to the cannon is much larger because the cannonball has less mass.
What is the force experienced when a boxer moves into an oncoming punch?
The force is increased since the time is shortened.
How is the force due to gravity affected when the block of ice it acts on slides down a ramp?
The force of gravity remains the same no matter what the orientation the moving object has.
If an action force in baseball is the force of the bat against the ball, what is the reaction force?
The force of the ball against the bat.
If a pair of toy freight cars, one twice the mass of the other, fly apart when a compressed spring that joins them is released, which of the two receives the greater force exerted on it?
The forces they experience are the same (Newton's 3rd Law equal and opposite), but the acceleration of the two are different since each is a different mass.
What would be the momentum of the fragments of a cannonball that explodes following a parabolic path?
The fragments continue along the original path that they were following.
Why does a hockey puck sliding across the ice finally come to rest?
The friction it experiences from the ice, air, and its own weight bring it to a rest
What is the reaction force when a rocket exerts exhaust gases downward?
The gases push back against the rocket causing it to move upwards. The interaction is between the gases and the rocket.
How do the number of items you have running on your car impact your fuel consumption?
The greater the number of items running the greater your fuel consumption.
Rotational Inertia, Continued-1
The greater the rotational inertia, the harder it is to change its rotational state. A tightrope walker carries a long pole that has a high rotational inertia, so it does not easily rotate. Keeps the tightrope walker stable.
The winner of a game of tug of war exerts the greatest force on what?
The greatest force is exerted on the ground.
What must one's hand do to make a karate chop more effective based on our understanding of momentum?
The hand must bounce upon impact.
How is the balance of a tightrope walker affected by the pole they carry
The heavier the pole, the greater the rotational inertia of the pole, therefore the better balance the tightrope walker will have.
What is the impulse of a truck that comes to a stop by crashing into a haystack vs. crashing into a brick wall?
The impulse is the same even though the elements of Force and time are different.
Why can a sheet of paper can be quickly jerked beneath a container of milk without toppling?
The inertia the container of milk has causes it to want to stay in place.
What is the reaction force on a ball as it falls to Earth if the action force is the Earth's pull on the ball?
The interaction is between the ball and the Earth. So if the Earth pulls on the ball, the ball must pull back on Earth.
Conservation of Angular Momentum
The law of conservation of angular momentum states: If no external net torque acts on a rotating system, the angular momentum of that system remains constant. Analogous to the law of conservation of linear momentum: If no external force acts on a system, the total linear momentum of that system remains constant.
Center of Gravity—Stability
The location of the center of gravity is important for stability. If we draw a line straight down from the center of gravity and it falls inside the base of the object, it is in stable equilibrium; it will balance. If it falls outside the base, it is unstable.
How does the mass of an apple on the moon compare with that on Earth?
The mass of an object is the same anywhere in the universe (the amount of matter it is made up of does not change). It's weight is different because it is subject to the force of gravity wherever it is.
If a same-size iron ball and wooden ball are dropped simultaneously from a tower and reach the ground at the same time, what is greater about the iron ball?
The momentum it has.
What happens to the momentum of an airplane when bullets are fired from it in the forward direction?
The momentum of the plan would have to decrease.
What is measured at zero if a car travels around a circular track at a constant speed?
The net force acting on it is 0, however its acceleration & velocity are not because it is constantly changing direction.
Where is the net force on any object in equilibrium?
The net force is 0
If an object is suspended at rest holding a rope with one hand and the side of wall with the other, what do you know about the force vectors that act on it?
The net force is 0. The object is at rest and is in static equilibrium.
What is the net force on any object in equilibrium?
The net force is always zero
In which direction is the net force exerted on a car working if the car is traveling in a circular path at a constant speed
The net force is working inward Toward the center of the curve - centripetal force.
How does the normal force on an object change as the ramp it is sitting on is raised?
The normal force gets smaller and smaller as the steepness of the incline increases.
When does a vehicle undergo acceleration?
The object is changing speed or changing direction
Whirl a rock at the end of a string and it follows a circular path. If the string breaks, what kind of path will the rock have the tendency to continue in?
The object will travel in a tangent from the circular path it had before the string broke. In other words it will travel in a straight line from the point at which the string broke.
If an object - one filled with water, the other with ice were rolled down an incline which one would take the least amount of time to get to the bottom
The object with liquid water.
What causes an object to have GPE?
The object's location (height) above the ground.
If an object moves with a constant acceleration, what is its velocity?
The object's velocity is increasing by the same amount every second it is in motion.
An object with a large concentration of mass located at one end is dropped to the floor. In which orientation would it fall faster
The one in which the mass is oriented closest to the object's point of rotation.
If two freight trains roll along a pair of tracks with the same speed but one has twice as much mass, what is true of their momentum?
The one with twice as much mass has 2 x the momentum.
How does the speed of a Ping-Pong ball compare to a golf ball if they are both moving in the same direction with the same amount of KE?
The ping pong ball must be moving faster since its mass is less. That is the only way it could have the same KE as a golf ball.
When a baseball player catches the ball in their glove the action force is the force of the ball against the glove. What is the reaction force?
The reaction force is the glove pushing back against the ball.
What is the resultant in a system in mechanical equilibrium
The resultant would be zero (doesn't move)
Rotational Inertia, Continued-3
The rotational inertia depends upon the shape of the object and its rotational axis.
If the rotational speed of an object is doubled, how is the linear speed of something sitting on that object affected
The rotational speed of the object is doubled as well
What happens to the speed of the rotation of a cloud of particles in space that gravitate together forming an increasingly dense ball that shrinks in size
The rotational speed will increase if all those particles go closer and closer together
Burl and Paul paint signs together on a scaffold. Compared to their individual weights plus the weight of the scaffold, what is the sum of the tensions in the supporting ropes?
The same
Burl and Paul paint signs together on a scaffold. Compared to their weights plus the weight of the scaffold, the sum of tensions in the supporting ropes is?
The same
If Burl carries Paul piggy-back while standing in the middle of a scaffold, what would the tensions in the two supporting ropes be?
The same
What would the skidding distance be of a truck that has twice the mass of another truck?
The same
What is the magnitude of the force on someone's hand if they execute a swift blow to a cement block and break it?
The same as the amount of the force applied to the block.
What are two factors that greatly affect air resistance?
The speed of the object and the size of its frontal surface area.
What measurement does the speedometer of an automobile read?
The speed the car is going at any given instant
Three objects roll down a hill - disk, ring, and sphere. Which reaches the bottom first
The sphere will reach the bottom of the hill first, then the disk and finally the ring will be last
What is true of the stopping force of a truck that comes to a stop after crashing into a haystack vs. a brick wall?
The stopping force is greater for the brick wall.
What would be true of the target and the shooter if a tiny gun made of strong but very lightweight material fires a bullet more massive than the gun itself?
The target would be safe than the shooter since the shooter would be subject to the mass of the bullet.
Torque
The tendency of a force to cause rotation is called torque. Torque depends upon three factors: Magnitude of the force The direction in which it acts The point at which it is applied on the object
If Burl carries Paul piggy-back while standing in the middle of a scaffold, what would the tensions of the two supporting ropes be?
The tensions in the two ropes should be the same. Half of the combined weight of Burl and Paul
Why does extending your hand forward before catching a fast moving ball increase the impact force and letting your hand ride backward with it reduce the force of contact on your hand?
The time of contact is increased.
Why is the force experienced reduced when a boxer moves away from a punch?
The time of contact is increased.
If a heavy truck and a small car roll down a hill a the same time at the same speed, and are forced to stop in the same amount of time, which requires greater force?
The truck requires greater force because it has more mass.
What do we learn from the fact that the Moon pulls on the Earth and the Earth pulls back on the Moon?
The two make up a system/interaction that constitutes an action/reaction pair.
You cannot exert a force on a wall unless what happens?
The wall must push back against you with an equal and opposite force.
If the outer track on a railroad track is longer, what does that cause the wheel that rides on it to need to do
The wheel on the outside has to go faster Those wheels will have to travel faster at a greater distance to maintain speed with the wheels on the inner track.
How does the tangential speed of a wide part of a railroad wheel compare to a narrow part
The wide part of the railroad wheel will move faster than the narrow part The narrow part has a smaller tangential speed.
What happens to the rotational speed of a figure skater as they bring their arms in close to their body
Their rotational speed increases
If two people balance a seesaw and one of the people leans inward toward the center what happens to their end of the seesaw
There end would rise
Due to inertia, a railroad train in motion should continue moving indefinitely when its engine is turned off. Why is that not the case?
There is a friction force between the wheels and rails, air resistance force at work when train moves
Due to inertia, a railroad train in motion should continue moving indefinitely when its engine is turned off. Why is that not the case?
There is a friction force between the wheels of the train and the rails. There is also air resistance (another friction) force at work on the train as it moves.
What would be the difference in net recoil between throwing a heavy ball while standing on rollers skates vs. going through the motions of throwing the ball but holding onto it?
There is no difference since the net momentum is 0.
Why does centripetal force do no work on a circular moving object
There is no force vector component in the direction the object is traveling. The force is all directed toward the center.
When you apply brakes to a speeding bicycle, KE is transformed into what?
Thermal energy (heat) from the friction of the brakes.
How does a ball's initial speed and its final speed compare when it is thrown upwards and returns to the same location?
They are identical because the rate of deceleration it experiences goes upwards is equal to its rate of acceleration heading to the ground
How does a ball's initial speed and its final speed compare when it is thrown upwards and returns to the same location?
They are identical because the rate of deceleration it experiences going upwards is equal to its rate of acceleration heading to the ground.
Which produces more force: driving into a very massive concrete wall with no "give," or having a head-on collision with an identical car moving toward you at the same speed?
They are the same
When no forces act on moving objects what normally happens to their paths?
They continue to follow a straight line path
Does standing on the floor being pulled downward by gravity and being supported upward by the floor constitute an action/reaction pair of forces?
They do not because they are not part of the same interaction. The reaction force to being pulled by gravity is you pulling back on gravity.
What is the relationship in acceleration if two bullets fall into a river from a very high bridge if one is dropped from the bridge and the other is fired from it?
They will both accelerate at the same rate. Their speeds will be different from each other but not their rate of acceleration.
What will happen to an astronaut if they throw a baseball at 20 m/s away from their body?
They will move in the opposite direction at a lower speed.
If a seesaw is going to be balanced, where would someone have to sit if the person across from them is 3 times heavier
They would have to sit 1/3 of the distance away.
Where would you want to kick a football to ensure it won't rotate end over end
Through its center of gravity
Where do you kick a football if you do not want it to rotate?
Through the CM
Why do you "choke up" on a baseball bat?
To decrease Rotational inertia
Why do you bend your knees when you run?
To decrease rotational inertia
Center of Mass and Center of Gravity, Continued
To determine the center of gravity, suspend the object from a point and draw a vertical line from suspension point. repeat after suspending from another point. The center of gravity lies where the two lines intersect.
Why does a tightrope walker carry a pole when they are walking?
To increase rotational inertia and lower CM
Simulated Gravity, Continued
To simulate an acceleration due to gravity, g, which is 10 m/s^2 a space station must have a radius of about 1 km (i.e. diameter of 2 km). rotate at a speed of about 1 revolution per minute.
What did Galileo's use of inclined planes allow him to do?
To slow down the ball's change in speed by changing the angle that inclined planes were set at
Pulling slowly on the bottom string tied to a heavy ball hanging by a string above it breaks which of the two strings?
Top string
What makes you fall forwards when you try to touch your toes when your heels are against a wall?
Torque
What does torque involve compared to a force
Torque is about rotation, leverage, and the distance of the lever arm Torque also involve a lever distance
What happens when an object's base is not below the CM?
Torque is produced
Formula for torque
Torque=Fl
What is the total kinetic energy of two objects that collide if one has a KE of 25 J and the other has a KE of 50 J just before they collide?
Total KE = KE1 + KE2= 75 J
An object with a large amount of rotational inertia would have a majority of its mass located where
Towards the outside
How does the amount of work compare between lifting a 1000-kg car and a 2000-kg car?
Twice as much work
If one golf cart out of two identical ones has twice the speed, what do you know about its KE?
Two times the speed equals how much of a change in KE? Four times as much.
How temperature effects Gas experiment
Use water bath to vary the temperature Calculate the volume of air in test tube before heating Measure volume of air after heating Use a narrow glass tube with liquid above the air so you can clearly see how it has expanded
Efficiency =
Useful Energy Output / Total Energy Input
Vector quantity and non-vector quantities
Vector quantity- magnitude and direction Scalar quantity- magnitude (speed)
Transverse Wave
Vibrations are at 90° to the direction energy is transferred
Longitudinal Waves
Vibrations are parallel to the direction the wave transfers energy
Which vehicle undergoes the greatest change in velocity if a Mack truck and a Volkswagen traveling at the same speed have a head-on collision?
Volkswagen
Electromagnetic Waves
Waves have different wavelengths - continuous spectrum All transverse - Travel at same speed through a vacuum
How does the time change of a falling object if you add weight to the top of the object
Weight at the top of the object causes it to fall slower. Weight closest to the bottom of the object causes it to fall faster.
Centripetal Force—Example
When a car rounds a curve, the centripetal force prevents it from skidding off the road. If the road is wet, or if the car is going too fast, the centripetal force is insufficient to prevent skidding off the road.
What happens to the acceleration of an object when it reaches its terminal velocity?
When an object reaches terminal velocity it is no longer accelerating. Therefore its acceleration is 0.
Circular Motion
When an object turns about an internal axis, it is undergoing circular motion or rotation. Circular Motion is characterized by two kinds of speeds: tangential (or linear) speed. rotational (or circular) speed.
When do you have smaller rotational inertia?
When mass is close to the axis
When do you have a larger rotational Inertia?
When mass is far from the axis
How does the concentration of mass effect where an object's center of gravity is
Where the concentration (Center of mass) of mass is the center of gravity tends to be.
Renewable Energy
Wind Farms Geothermal Energy Solar Energy Hydroelectric Power
Energy Transfer =
Work Done
Dangers of Microwaves
Yeah human body tissue internally
Earth continually moves about 30 km/s through space, which means the wall you stand next to also is moving at 30 km/s. When you jump vertically the wall doesn't slam into you because
You and the wall are in the same system so you are moving at the same speed the wall is
Earth continually moves about 30 km/s through space, which means the wall you stand next to also is moving at 30 km/s. When you jump vertically why doesn't the wall slam into you?
You and the wall are in the same system so you are moving at the same speed the wall is even when you are in the air.
If bending your knees when you land after jumping off of an elevated position changes the time of contact by a factor of 10 compared to being stiff-legged, what does that do to the average force your body experiences?
You experience 1/10 of the force.
What must someone do to get an object to rotate
You must apply torque (external force)
Would you agree with your friend if they stated that the heavyweight champion of the world cannot exert a 50 N force on an isolated piece of tissue paper?
You would agree since the heavyweight champion of the world can only exert as much force as the tissue paper can apply back against him.
To do somersaults, what position would your body need to be in to rotate easier
Your body needs to be in a circular position. Put the mass as close to the middle as possible. Curled up in a ball
While you are standing in the aisle of a bus, the driver suddenly makes a left turn. You lurch to the right due to
Your body wants to remain in the location where it was because inertia
The skydiver steps from a helicopter and falls for a few seconds until terminal velocity is reached. Thereafter, until he opens his parachute, his acceleration *
Zero
What is a cart's acceleration if it maintains a constant velocity of 100 m/s for 10 s?
Zero
A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, how many force would be required to keep the puck sliding at constant velocity?
Zero, in the absence of friction and air resistance, the puck will continue indefinitely
how does a linear force create rotation
a force applied away from axis of rotation will rotate the object about the axis
leverage
a lever amplifies an input/applied force to provide a greater output/resistance force to provide leverage
levers
a relatively rigid body that may be made to rotate about an axis by the application of a force
revolutions
a single rotation about an axis
angular motion and law of acceleration
a torque applied to a body causes an angular acceleration of that body of a magnitude proportional to the toque in the direction of the toque, inversely proportional to the body's moment of inertia
torque is
a vector quantity, direction is defined by the angular movement created, CW or CCW, measured in Nm
What is a bungee jumper's average deceleration if they attain a speed of 30 m/s just as the bungee cord begins to stretch which lasts 2 s?
a= change in velocity/time then you have to factor in gravity and divide your answer= 1.5 g
camera is in frontal plane, anteriorposterior axis
abduction, adduction, roll
If you double the net force on an object what also doubles?
acceleration
What happens to a skydiver's acceleration as their velocity of fall increases?
acceleration goes down because they are closer to terminal speed / velocity
What happens to the acceleration of an object that experiences a tripling of its net force?
acceleration triples
centric forces
act at the center of the system, result in linear motion
eccentric forces
act off center on a system, result in rotation and curvilinear motion
balance
an even distribution of weight enabling someone or something to remain upright and steady, static concept
axis of rotation is
an imaginary line, that can found inside or outside of the system
goinometer
an instrument that measures an angle
axis of rotation, fulcrum, pivot point
anchor point of system
internal angle
angle formed inside the joint
if radius of gyration decreases
angular velocity increases, bring limbs close together allows us to spin more in figure skating
total angular momentum
angular velocity of arms and legs must be larger than the trunk and head to stabilize body position in the air
degrees
arbitrary unit of measurement
tangential linear velocity and acceleration of a point on a rotating object
are proportional to radius of rotation
base of support
area bound by the outermost regions of contact between body and support surface
improvement comes from
attention to detail
body angles
axis of rotation is no fixed because the longitudinal segments shifts position because the axis migrates
fulcrum
axis of rotation, pivot point
What will happen to a ball when you quickly jerk a cart forward that has the ball resting in the middle?
ball hits the back of the cart
factors affecting stability
base of support, position of center of gravity, and mass
instant center
because axis of rotation is not fixed in human body since its difficult to locate the precise location of the instant center, we estimate joint positions when analyzing human movements