Physics Final
When setting up projectile motion questions, what is an important characteristic of projectile motion to keep in mind?
1. Although the horizontal and vertical motions of a projectile are independent, they are connected through the time dt that the object is in the air. 2. Projectile motion is made up of two independent motions: uniform motion at constant velocity in the horizontal direction and free-fall motion in the vertical direction
Newton's law of gravity describes the gravitational force between____
1. Earth and sun 2. Sun and planets 3. Earth and moon 4. Person and earth
How many times per day does the International Space Station-or any satellite in a similar low orbit-go around the earth?
15
A tiger is running in a straight line. If we double both the mass and speed of the tiger, the magnitude of its momentum will increase by what factor?
4
(True or False) If the sum of both the external torques and the external forces on an object is zero, then the object must be at rest
False
(True or False) If the sum of the external forces on an object is zero, then the sum of the external torques on it must also be zero
False
(True or False) If the sum of the external torques on an object is zero, then the sum of the external forces on it must also be zero
False
An object is in static equilibrium if____
Fnet=0 and Tnet=0
Jonathan accelerates away from a stop sign with his daughter in the passenger seat. On whom does the back of the seat exert a greater force?
Jonathan
Given how the quantity work-which has units of energy-was defined, another unit for energy, equivalent to the joule (J), is____
Nm
The slope at a point on a position vs. time graph of an object is the_____
Object's instantaneous velocity at that point
A baseball bat has a thick, heavy barrel and a thin, light handle. What should you do if you want to hold a baseball bat on your palm so that it balances vertically?
Put the end of the handle in your palm, with the handle up.
You have 2 identical-looking metal spheres of the same size and mass. One is solid, one is hollow. How could you determine which is which?
Spin the spheres. If the torque is the same, sphere getting larger angular acceleration would be the solid one
Josh and Taylor, standing face-to-face on frictionless ice, push off each other, causing each to slide backward. Josh is much bigger than Taylor. After the push, which of the two is moving faster?
Taylor
When a car is weighted, it is driven slowly on a horizontal floor over a scale that records a reading as the front wheels go over the scale, and then records a second reading as the rear wheels go over the scale. The weight of the car is equal to_____
The sum of the two weights
For an object in uniform circular motion, what can you say about the directions of the velocity, acceleration, and net force vectors?
The velocity vector is perpendicular to the acceleration vector; the acceleration vector is parallel to the net force vector
When a rigid object rotates about a fixed axis, what is true about all the points in the object?
They all have the same angular speed
Dave pushes his son across the snow on a sled. As Dave pushes, his son speeds up. What can be said about the two forces?
They have the same magnitude
(True or False) If an object remains at rest, then the sum of both the external torques and external forces on the object must be zero
True
What a hockey puck sliding in a straight line at a constant speed an example of?
Uniform Motion
What is the difference between speed and velocity?
Velocity contains information about the direction of motion while speed does not
A skydiver has his parachute open and is floating downward through the air at a constant speed. What are the forces acting on the skydiver-parachute?
Weight, air resistance
A very rigid material- one that stretches or compresses only slightly under large forces-has a large value of______
Young's Modulus
You must lean quite far forward as you rise from a chair. Why?
Your center of gravity must remain over a region of support (your feet). As you rise your rear end is behind your feet so you must lean forward to compensate
For motion with constant, nonzero acceleration, the position vs. time graph has the shape of____
a parabola
Hooke's law describes the force of_____
a spring
A ball dropped from a height during its downward motion is an example of....
a vertical motion with a negative velocity and a negative acceleration
A ball thrown upward, before it starts to fall back down is an example of....
a vertical motion with a positive velocity and a negative acceleration
If we solve the formula for centripetal acceleration____, for v, we have:_____
a=(v^2)/r, v=sqrt(ar)
The action/reaction pair of forces____
acts on two different objects
If an object is in uniform motion, the dots on a motion diagram___
are spaced at equal distances apart
A pilot drops a weight from a plane and looks down after she drops it, where is the plane located at the instant the weight hits the ground?
directly over the target
In the impulse approximation,_____
external forces can be neglected during the time the impulsive forces acts
When a car turns a corner on a level road, which force provides the necessary centripetal acceleration?
friction
A toy on a spring illustrated energy conversion among what different forms?
gravitational potential energy, kinetic energy, and elastic potential energy
When a barrel is full it has a much_____moment of inertia and resistance to changes in its rotation, so it will be____stable moving platform than the empty barrel
greater, more
The acceleration down the slope is given by_____if the friction is neglected.
gsin(theta)
If you are traveling at the greatest speed which is sae, then you are accelerating at the____acceleration which is safe. Now if the radius is reduced, this tends to____the acceleration above safe values. To bring it back down, your speed should be____
highest, increase, reduced
The total momentum of a system is conserved_____
if no external forces act on the system
Why is it impossible for an astronaut inside an orbiting space station to go from one end to the other by walking normally?
in an orbiting station, after one foot pushes off there isn't a force to bring the astronaut back to the "floor" for the next step
Velocity vectors point___
in the same direction as displacement vectors
If a system is isolated, the total energy of the system____
is constant
The acceleration vector of a particle in projectile motion_____
is directed down at all times
For uniform circular motion, the acceleration____
is directed toward the center of the circle
If you hold a heavy weight over your head, the work you do____
is zero
An object will be stable if_____
its center of gravity lies over its base of support
The unit of work is the___
joule
If you are performing the weightlifting exercise known as the strict curl, the tension in your biceps tendon is_____
larger than the weight you are lifting
The lower the angle of the slope, the_____ the acceleration along the ramp, therefore the speed at the bottom of a slope will be _____, and, consequently, the control will be better
lower, lower
The units of acceleration are
m/s/s
The____of a vector is always a positive quantity
magnitude
The correct SI units for distance and mass are___ and ___
meters/kg
An object's angular momentum is proportional to its____
moment of interia
In an inelastic collision,____
momentum is conserved
If an object is rotating clockwise, this corresponds to a_____angular velocity
negative
If you throw a ball against the ceiling-so the ball moves upward and then rebounds to move downward-at the instant the ball hits the ceiling, the acceleration is_____
negative
Alyssa pushes to the right on a filing cabinet; the friction force from the floor pushes on it to the left. Because the cabinet doesn't move, these forces have the same magnitude. Do they form an action/reaction pair?
no
Suppose two vectors have unequal magnitudes, can their sum be 0?
no
If Sam walks 100 m to the right, then 200 m to the left, his net displacement vector___
points to the left
The acceleration vector of a particle in uniform circular motion____
points toward the center of the circle
From somewhere in space the N. pole is viewed. A point on Earth's equator would have a______angular velocity due to the earth's rotation.
positive
If you raise an object to a greater height, you are increasing its____
potential energy
As one stretches a metal wire does it reach the breaking point, proportional limit, or elastic limit first?
proportional limit
The acceleration that an object experiences is____
proportional to the net force, inversely proportional to the mass
The angular displacement of a rotating object is measured in______
radians
to make a tighter turn with a smaller radius, you need to_____your speed
reduce
So if we take a turn with a radius which is 4x smaller, we need to_____ our speed_____
reduce, in 2x
Ax is positive if is directed____; Ay is positive if is directed_____
right/up
Springs can stretch; so can different materials, including:
rubber, glass, steel
making rough estimates of physical quantities is useful___
so that you can see if the answer to a problem makes physical sense
In uniform motion, what quantities are constant?
speed, the magnitude of the net force
The acceleration of a cart rolling down a ramp depends on______
the angle of the ramp
A net torque applied to an object causes______
the angular velocity of the object to change
Impulse is
the area under the force curve in a force vs. time graph
The reason an astronaut in an earth satellite feels weightless is that___
the astronaut is falling
If you kick a ball, you apply an impulse. The impulse is equal to
the change in momentum of the ball
The area under a velocity vs. time graph of an object is___
the displacement of the object
If you stand on a trampoline, it depresses under your weight. When you stand on a hard stone floor_____
the floor deforms-very slightly-under your weight
Two forces produce equal torques on a door about the hinge. One is applied at the midpoint and the other at the knob. Which has a greater magnitude?
the force at the midpoint
When using the law of conservation of energy, we consider:
the initial total energy of the system equals the final total energy of the system
You are cycling around a circular track at a constant speed. Does the magnitude of your acceleration change?
the magnitude of the acceleration doesn't change, but the direction does
When we say that momentum is "conserved," we mean_____
the momentum of an isolated system is constant
For an object to be in static equilibrium, the net force must be equal to zero and____
the net torque must be equal to zero
Which factor does the torque on an object NOT depend on?
the object's angular velocity
When we draw a diagram of the forces acting on an extended object, the tail of the force vector for the weight should be at_____
the object's center of gravity
Moment of inertia is_____
the rotational equivalent of mass
Is the spring constant of smaller springs larger, smaller, or the same as the spring constant of the original spring (cut in half)?
the spring constant of each half will be 2x the spring constant of the original long spring since it will stretch only half as much under the same tension
A 1 lb ball and a 100 lb ball are dropped from a height of 10 feet at the same time. In the absence of air resistance____
the two balls end in a tie
Consider two graphs of velocity versus time for two objects in free fall. What can we say about the graphs?
the two graphs have the same slope and they are both straight lines
You toss a basketball toward the basket. At the highest point of its arc_____
the vertical component of the velocity is zero
Astronauts on the International Space Station feel weightless because____
their apparent weight is zero
A skydiver has reached terminal velocity-she now falls at a constant speed, so her acceleration is zero. Is there a net force on her? If so, what is the direction?
there is no net force
A gun with a very long barrel is used, why?
to allow the force of the expanding gases from the gunpowder to act for a longer time
An object in circular motion has velocity that is constantly changing. The direction of the acceleration is______
toward the center of the circle
A car rounding a corner and a car going over a crest of a hill are both examples of____
uniform circular motion
If you are standing on the floor, motionless, what are the forces that act on you?
weight force and normal force
A basketball player is getting ready to jump, pushing off the ground and accelerating upward. What are the forces acting on the basketball player?
weight, normal
What is an energy transfer?
work
If you are not wearing a seatbelt and the car you are driving hits a fixed barrier, you will hit the steering wheel with some force. This is because____
you continue moving even after the car has stopped
