Unit 2 test physics
Newton's 2nd law
The impulse-momentum relationship is a direct result of
Twice as much work
A 1000-kg car and a 2000-kg car are hoisted to the same height. Raising the more massive car requires
3 m/s
A 4 kg ball has a momentum of 12 kg m/s. What is the ball's speed?
5/6 m/s
A 5-kg fish swimming at 1 m/s swallows an absent minded 1-kg fish at rest. The speed of the larger fish after lunch 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
2/3 m/s
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
16 kg
A ball is moving at 3 m/s and has a momentum of 48 kg m/s. What is the balls mass?
less than 100J
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.
The bottom
A ball rolling down an incline has its maximum kinetic energy at
At the top of the incline
A ball rolling down an incline has its minimum speed
16 times the KE
A car moves 4 times as fast as another identical car. Compared to the slower car, the faster car has
doubled
A freight train rolls along a track with considerable momentum. If it were to roll at the same speed but had twice as much mass, its momentum would be
none of the above
A heavy and a light object released from the same height in a vacuum have equal
Greater
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 to the force that stops the car, the force needed to stop the truck is
Always false
A hydraulic press, like an inclined plane, is capable of increasing energy
50%
A jack system will increase the potential energy of a heavy load by 1000 J with a work input of 2000 J
Power
A job is done slowly, while an identical job is done quickly. Both jobs require the same amount of work, but different amounts of
more
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, it's muzzle velocity would be
none of the above choices
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
10%
A machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is
1 unit
A piece of putty moving with 1 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 a combined momentum of
rifle has much more mass than the bullet.
A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the
Moving
An object that has kinetic energy must be
1 kg m/s
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
1/6 m/s
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 thereafter is
20 N
Consider a hydraulic press. When the input piston is depressed 20 cm, the output piston is raised 1 cm.
1/6 m/s
Consider massive gliders that slide friction free along a horizontal air track
zero
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
Decreased
When bullets are fired from an airplane in the forward direction, the momentum of the airplane will be
Long time
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
distance that a force acts
Whereas impulse involves the time that a force acts, work involves the
Momentum
If an object has kinetic energy, then it also must have
Twice as much
If an object is raised twice as high, its potential energy will be
Momentum
If the speed of a moving object doubles, which of the following also doubles
three times the usual power output.
If you do work on an object in one-third the usual time, your power output is
The change in momentum it produces
It is correct to say that impulse is equal to
10N
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
greater than that of the apple only if the apple bounces
Momentum is transferred to the ground when an apple falls on it. The momentum absorbed by the ground is
the force on the ball is at right angles to the ball's motion
No work is done by gravity on a bowling ball that rolls along a bowling alley because
The top
The ball rolling down an incline has its max potential energy at
6
The change in momentum, in kg m/s, 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 is
Both requires the same amount of work
What task requires the most work; lifting a 50-kg sack 2 meters or lifting a 25-kg sack 4 meters?
no work on the wall is done in either case.
If you push for a half hour or a whole hour against a stationary wall
Newton's Third Law
The conservation of momentum is most closely related to
all of these
The force on an apple hitting the ground depends upon
0
Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet
all of these
Two objects have the same size and shape, but one is 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
Heat
When an automobile is braked to a stop, it's kinetic energy is transformed to
None of the above could be zero
When an object is in motion, which of the following could not have a value of zero?
about 1/10 as great
When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, you make the time of the impact about 10 times as great as for a stiff-legged landing. In this way the average force your body experiences is
The 60 km/hr car
Which has greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60 km/hr?
Slowing down from 100 km/h to 70 km/h
Which requires the most amount of work by the brakes of a car?
180 m
A car traveling at 50 km/h will skid 20 m when its brakes are locked. If the same car is traveling at 150 km/h, what will be its skidding distance?
The same
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 a 50-kg sack is
The same as it's potential energy
After rolling halfway down an incline, a marbles kinetic energy is
potential energy
An object at rest may also have
Location
An object may have potential energy because of its
the target would be safer than the shooter
Suppose that a tiny gun made of a strong but very light material fires a bullet that is more massive than the gun itself. For such a weapon
Half as much
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
Unchanged
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
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
time of impact is increased
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 on the player's hand principally because the
both the same
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
