Physics Practice Test

Recoil is noticeable if we throw a heavy ball while standing on roller skates. If instead we go through the motions of throwing the ball but hold onto it, our net recoil will be

zero

Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet?

0

A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5-kg bowling ball initially at rest. The bowling ball and putty then move with a momentum of

1 kg m/s

A piece of putty moving with one unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. After the putty sticks to the ball, both move with combined momentum of

1 unit

A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5-kg bowling ball that is initially at rest on a frictionless surface. The speed of the putty after is

1/6 m/s

A 5-kg shark swimming at a speed of 1 m/s swallows an absent-minded 1-kg fish swimming toward it at 4 m/s. The speed of the shark after this meal is

1/6 m/s

Consider massive gliders that slide friction-free along a horizontal air track. Glider A has a mass of 1 kg, a speed of 1 m/s, and collides with Glider B that has a mass of 5 kg and is at rest. If they stick upon collision, their speed after collision will be

1/6 m/s

It takes 40 J to push a large box 4 m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box?

10 N

A machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is

10%

A ball is moving at 3 m/s and has a momentum of 48 kg m/s. What is the ball's mass?

16 kg

A car moves 4 times as fast as another identical car. Compared to the slower car, the faster car has

16 times the KE

A 5000-kg freight car moving at 2 m/s runs into a 10,000-kg freight car at rest. They couple upon collision and move away as one body at

2/3 m/s

Consider a hydraulic press. When the input piston is depressed 20cm, the output piston is observed to move 1 cm. On the same press, an input force of 1N can raise no more than

20N

A 4kg ball has a momentum of 12kg m/s. what is the ball's speed?

3 m/s

A 5-kg fish swimming at a speed of 1 m/s swallows an absent-minded 1-kg fish at rest. The speed of the larger fish after this lunch is

5/6 m/s

A jack system will increase the potential energy of a heavy load by 1000 J with a work input of 2000 J. The efficiency of the jack system is

50%

The change in momentum, in kg m/s that occurs when a 1.0 kg ball travelling at 4.0 m/s strikes a wall and bounces back at 2.0 m/s is

6

A car moving at 50 km/hr skids 20 m with locked brakes. How far will the car skid with locked brakes if it were traveling at 100 km/hr?

80 m

When bullets are fired from an airplane in the forward direction, the momentum of the airplane is

decreased

Whereas impulse involves the time that a force acts, work involves the

distance that a force acts

A freight train rolls along atrack with considerable momentum. If it rolls at the same spped but has twice as much mass, its momentum is

doubled

A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time. Compared with the force that stops the car, the force needed to stop the truck is

greater

Momentum is transferred to the ground when an apple falls on it. The momentum absorbed by the ground is

greater than that of the apple only if the apple bounces.

A clerk can lift containers a vertical distance of 1 meter or can roll them up a 2 meter-long ramp to the same elevation. With the ramp, the applied force required is about

half as much

When an automobile is braked to a stop, its kinetic energy is transformed to

heat

A ball is projected into the air with 100 J of kinetic energy which is transformed to gravitational potential energy at the top of its trajectory. When it returns to its original level after encountering air resistance, its kinetic energy is

less than 100 J

An object may have potential energy because of its

location

When you are in the way of a fast-moving object and can't get out of its way, you will suffer a smaller force of impact if you decrease its momentum over a

long time

If an object has kinetic energy, then it also must have

momentum

If the speed of a moving object doubles, which of the following also doubles?

momentum

Two objects have the same size and shape, but one is much heavier than the other. When they are dropped simultaneously from a tower, they reach the ground at the same time, but the heavier one has a greater

momentum

A large metal ball is shot from a cannon with a short barrel. If the same ball were to be shot from cannon with a longer barrel, its muzzle velocity would be

more

An object that has kinetic energy must be

moving

The impulse-momentum relationship is a direct result of

newtons 2nd law

The conservation of momentum is most closely related to

newtons 3rd law

If you push for a half hour or a whole hour against a stationary wall

no work on the wall is done in either case

A light aluminum ball and a heavy lead ball of the same size are allowed to roll down an incline. When they are halfway down the incline, they will have identical

none of the above choices

When as object is in motion, which of the following could not have a value of zero?

none of the above could be zero

An object at rest may also have

potential energy

A job is done slowly, while an identical job is done quickly. Both jobs require the same amount of work, but different amounts of

power

A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the

rifle has much more mass than the bullet

Which requires the most amount of work by the brakes of a car?

slowing down from 100 km/h to 70 km/h

Which has greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60 km/hr?

the 60 km/hr car

A ball rolling down an incline has its maximum kinetic energy at

the bottom

It is correct to say that impulse is equal to

the change in momentum it produces

No work is done by gravity on a bowling ball that rolls along a bowling alley because

the force on the ball is at right angles to the ball's motion

Both a 50-kg sack is lifted 2 meters from the ground and a 25-kg sack is lifted 4 meters in the same time. The power expended in raising the 50-kg sack is

the same

After rolling halfway down an incline, a marble's kinetic energy is

the same as its potential energy

The force on an apple hitting the ground depends on

the speed of apple before it hits the time of impact with the ground whether or not the apple bounces

Suppose a tiny gun made of a strong but very light material firs a bullet that is more massive than the gun itself. For such a weapon

the target would be safer than the shooter

A ball rolling down an incline has its maximum potential energy at

the top

If you do work on an object in one-third the usual time, your power output is

three times the usual power output

To catch a ball, a baseball player extends the hand forward before impact with the ball and then lets it ride backward in the direction of the ball's motion. Doing this reduces the force of impact of the players hand principally because the

time of impact is increased

If an object is raised twice as high, its potential energy will be

twice as much

A 1000-kg car and a 2000-kg car are hoisted the same distance. Raising the more massive car requires

twice as much work

If you push an object a given distance, while applying twice the force, you do

twice as much work

If you push an object twice as far while applying the same force, you do

twice as much work

If you find that twice as much work is needed to perform a task but it takes twice as much time, the amount of power required is

unchanged

When you jump from an elevated position you usually bend your knees upon reaching the ground, which makes the time of the contact about 10 times that of a stiff-legged landing. In this way the average force your body experiences is

about 1/10 as great

A heavy and a light object released from the same height in a vacuum have equal

accelerations

A hydraulic press, like an inclined plane, is capable of increasing energy

always false

A ball rolling down an incline has its minimum speed

at the top of the incline

What task requires the most work; lifting a 50-kg sack 2 meters or lifting a 25-kg sack 4 meters?

both require the same amount of work

Which would produce more force: driving into a very massive concrete wall with no give, or having a head on collision at the same speed with an identical car moving toward you with the same speed

both the same