Physics 1 concepts
A cart that is rolling at constant velocity on a level table fires a ball straight up. When the ball comes back down, will it land in front of the launching tube, behind the launching tube, or directly in the tube?
Directly in tube
3 factors that affects ability of force/torque to cause rotations
1)the magnitude of the force 2)the distance r from the point of application of the pivot 3) the angle at which the force is appliedu
Alice and Tom dive from an overhang into the lake below. Tom simply drops straight down from the edge, but Alice takes a running start and jumps with an initial horizontal velocity of 25 m/s. Neither person experiences any significant air resistance. Compare the time it takes each of them to reach the lake below.
Alice and Tom will reach the surface at the same time
A projectile is launched at an angle of 30 ∘ . Is there any point on the trajectory where v and a are perpendicular to eachother?
At the highest point
A cart that is accelerating on a level table fires a ball straight up. When the ball comes back down, will it land in front of the launching tube, behind the launching tube, or directly in the tube?
Behind the Tube
If the magnitude of vector A⃗ is less than the magnitude of vectorB⃗ , then the x component of A⃗ is less than the x component ofB⃗ .
False
In order to get an object moving, you must push harder on it than it pushes back on you.
False
The direction of a vector can be different in different coordinate systems.
False
The magnitude of a vector can be different in different coordinate systems.
False
A car is parked on a steep hill. What forces are present?
Force of gravity, friction, and normal force
A baseball player is sliding into second base. What forces are present?
Gravity, normal force, kinetic friction
angular momentum of particle in circular motion
L=mrv
Can the magnitude of the displacement vector be more than the distance traveled?
No
You're driving along the highway at a steady speed of 60 mph when another car decides to pass you. At the moment when the front of his car is exactly even with the front of your car, and you turn your head to smile at him, do the two cars have equal velocities?
No
When can we be certain that the average velocity of an object is always equal to its instantaneous velocity
Only when velocity is constant
Two ice skaters, Paula and Ricardo, push off from each other. Ricardo weighs more than Paula. Which skater, if either, has the greater speed after the push-off?
Paula
If an irregularly shaped object (such as a wrench) is dropped from rest in a classroom and feels no air resistance, it will
accelerate but will not spin
three balls are thrown off a cliff with same speed but different angles. Which has greatest impact speed?`
all have same
A golfer starts with the club over her head and swings it to reach maximum speed as it contacts the ball. Halfway through her swing, when the golf club is parallel to the ground, does the acceleration vector of the club head point straight down, parallel to the ground, approximately toward the golfer's shoulders, approximately toward the golfer's feet, or toward a point above the golfer's head?
approximately towards golfer's feet
An object is moving to the right, and experiencing a net force that is directed to the right. The magnitude of the force is decreasing with time. The speed of the object is
increasing
impulse
integral of force over a certain time
work
integral of force over certain distance
A baseball is thrown vertically upward and feels no air resistance. As it is rising
its momentum is not conserved, but its mechanical energy is conserved
A mosquito collides head-on with a car traveling 60 mph. Is the magnitude of the mosquito's acceleration larger than, smaller than, or equal to the magnitude of the car's acceleration?
larger than
A hand presses down on the book. Is the normal force of the table on the book larger than, smaller than, or equal to mg?
larger than mg
A 0.2 kg plastic cart and a 20 kg lead cart can both roll without friction on a horizontal surface. Equal forces are used to push both carts forward for a time of 1 s, starting from rest. After traveling 1 m, is the momentum of the plastic cart greater than, less than, or equal to the momentum of the lead cart?
less
Translational
measures an object's tendancy to resist a change in translational motion/velocity;mass
rotational
measures an object's tendancy to resist change in rotational motion/velocity; depends on where you apply force; moment of inertia
On a smooth horizontal floor, an object slides into a spring which is attached to another mass that is initially stationary. When the spring is most compressed, both objects are moving at the same speed. Ignoring friction, what is conserved during this interaction?
momentum and mechanical energy
inelastic collision
momentum is conserved but KE is not conserved, Total KE before collision is greater than after collision
Two ice skaters, Paula and Ricardo, push off from each other. Ricardo weighs more than Paula. Which skater, if either, has the greater momentum after the push-off?
momentum with same magnitude
Elastic Collision
momentum, PE, and KE are conserved
Two men, Joel and Jerry, push against a wall. Jerry stops after 10 min, while Joel is able to push for 5.0 min longer. Compare the work they do.
neither do any work
A small glider is coasting horizontally when suddenly a very heavy piece of cargo falls out of the bottom of the plane. You can neglect air resistance. Just after the cargo has fallen out
neither the cargo nor the plane change speed
A space shuttle astronaut is working outside the shuttle as it orbits the earth. If he drops hammer will it drop to earth?
no
If an object is at rest, can you conclude that there are no forces acting on it?
no
If the force on a particle at some point in space is zero, must its potential energy also be zero at that point?
no
If the potential energy of a particle at some point in space is zero, must the force on it also be zero at that point?
no
If you know all of the forces acting on a moving object, can you tell the direction the object is moving?
no
Must an object be rotating to have a moment of inertia?
no
Suppose two vectors have unequal magnitudes. Can their sum be zero?
no
static equlibrium
no net force and no net torque
A crate of fragile dishes is in the back of a pickup truck. The truck accelerates north from a stop sign, and the crate moves without slipping. Does the friction force on the crate point north or south? Or is the friction force zero?
north
angular momentum
perpindicular to plane of motion; torque causes change
power
rate of change of energy
Satellites in near-earth orbit experience a very slight drag due to the extremely thin upper atmosphere. These satellites slowly but surely spiral inward, where they finally burn up as they reach the thicker lower levels of the atmosphere. The radius decreases so slowly that you can consider the satellite to have a circular orbit at all times. As a satellite spirals inward, does it speed up, slow down, or maintain the same speed?
satellite speeds up
work and energy are..
scalar quantities
In uniform circular motion, which of the following are constant:
speed, angular velocity, and magnitude of net force
W<0
system does work on environment and system's energy decreases
A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car. During the collision
the forces are equal
Change in momentum is equal to
the impulse
If the torque on an object adds up to zero
the object is both accelerating and turning linearly
A process occurs in which a system's potential energy increases while the environment does work on the system. Does the system's kinetic energy increase, decrease, or stay the same? Or is there not enough information to tell?
there is not enough info
Consider a uniform solid sphere of radius R and mass M rolling without slipping. Which form of its kinetic energy is larger, translational or rotational?
translational energy is larger than rotational
Suppose you press your physics book against a wall hard enough to keep it from moving. In what direction does the friction force point
up
momentum is a
vector
The angular momentum of a system remains constant
when no torque acts on system
change in energy of the system is equal to
work
Can the magnitude of the displacement vector be less than the distance traveled?
yes
If a force is exerted on an object, is it possible for that object to be moving with constant velocity?
yes
If you set the cruise control of your car to a certain speed and take a turn, the speed of the car will remain the same. Is the car accelerating?
yes
Is it possible for the friction force on an object to be in the direction of motion?
yes
A box of mass m is pulled with a constant acceleration a along a horizontal frictionless floor by a wire that makes an angle of 15° above the horizontal. If T is the tension in this wire, then
T>ma
Alice and Tom dive from an overhang into the lake below. Tom simply drops straight down from the edge, but Alice takes a running start and jumps with an initial horizontal velocity of 25 m/s. Neither person experiences any significant air resistance. Just as they reach the lake below
THe speed of Alice is larger than that of tom
A string is attached to the rear-view mirror of a car. A ball is hanging at the other end of the string. The car is driving around in a circle, at a constant speed. Which of the following lists gives all of the forces directly acting on the ball?
Tension and gravity
torque due to gravity will cause object to rotate around axle
Tgrav=-Mgxcm; found by treating object as if all its mass were concentrated at the center of mass
A ball is thrown directly upward and experiences no air resistance.
The acceleration is downward during the entire time the ball is in the air.
elastic collision with both objects having same mass and object 2 is stationaryy
first ball stops and transfers all momentum to ball 2
rolling without slipping
friction force is negligible; translational + rotational KE; Vcm=Rw
A projectile is launched at an angle of 30 ∘ . Is there any point on the trajectory where v⃗ and a⃗ are parallel to each other? If so, where?
They are never parallel
If a force always acts perpendicular to an object's direction of motion, that force cannot change the object's kinetic energy.
True
The components of a vector can be different in different coordinate systems.
True
Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined plane and allowed to slide down from rest
Two objects reach bottom of incline at the same time
A roller-coaster car rolls down a frictionless track, reaching speed v0 at the bottom. If you want the car to go twice as fast at the bottom, by what factor must you increase the height of the track?
You must increase track height by a factor of 4
Net work is equal to
change in kinetic energy
non conservative force
depends on path; friction
conservative force
doesn't depend on path
As you are leaving a building, the door opens outward. If the hinges on the door are on your right, what is the direction of the angular velocity of the door as you open it?
down
torque
effectiveness of a force causing a rotation; rotational equivalent of a force; exerted about pivot point
W>0
environment does work on system and system's energy increases
A 0.2 kg plastic cart and a 20 kg lead cart can both roll without friction on a horizontal surface. Equal forces are used to push both carts forward for a time of 1 s, starting from rest. After the force is removed at t=1s, is the momentum of the plastic cart greater than, less than, or equal to the momentum of the lead cart?
equal
A mosquito collides head-on with a car traveling 60 mph. Is the force of the mosquito on the car larger than, smaller than, or equal to the force of the car on the mosquito?
equal
Is the earth's gravitational force on the sun larger than, smaller than, or equal to the sun's gravitational force on the earth?
equal
You drop a ball from a high balcony and it falls freely. Does the ball's kinetic energy increase by equal amounts in equal time intervals, or by equal amounts in equal distances?
equal amounts in equal distances
A small car has a head-on collision with a large truck. Which of the following statements concerning the magnitude of the average force due to the collision is correct?
experience the same average force
A car is being towed at constant velocity on a horizontal road using a horizontal chain. The tension in the chain must be equal to the weight of the car in order to maintain constant velocity.
false
As a tile falls from the roof of a building to the ground its momentum is conserved.
false
If two forces of equal magnitude act on an object that is hinged at a pivot, the force acting farther from the pivot must produce the greater torque about the pivot.
false
elastic collision with object 1 having greater mass and object 2 stationary
first ball keeps going with about same speed and ball 2 flies off with twice speed
elastic collision with object 2 stationary and with greater mass
first ball rebounds with about same speed and ball 2 barely moves
