Momentum & Energy

If you push against a stationary wall with great force for a half hour compared to the same force pushed for a whole hour, how much is work done?

0 work is done.

The power required to exert 1 N force, over a distance of 1 m in 1 second is? How many watts?

1 watt b/c work = 1 N x 1 m = 1mn 1mn/1 sec = 1 watt

Do 100 J of work in 50 sec and your power output is ... how many watts?

100J/50sec = 2 watts

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

16 times the kinetic energy

Two 5000 kg train cars roll without friction (one at 1m/s, the other at 2m/s) toward one another on a level track. They collide, couple(stick) and roll away together with a combined momentum of

5000 kg m/s

A bow is drawn so it has 60 J of potential energy. When fired, the arrow will ideally have a kinetic energy that is

60 J

Compared to the recoiling rifle, the bullet fired from the rifle has

a greater kinetic energy

Which of the following has the largest momentum relative to the Earth?

a pickup truck speeding along a highway

A feather and a coin dropped in a vacuum fall with equal

accelerations

A car has a head-on collision with another car that was approaching with the same magnitude of momentum. A third identical car driving with the same speed as the first car runs into an enormously massive concrete wall. Which of the four objects will experience the greatest impulse?

all will receive the same impulse

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

both have the same kinetic energy

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

both require same amount of work

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

distance that a force acts as

The force that accelerates a rock in outer space is exerted on the rocket by the

exhaust gases

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

greater

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

A bullet is fired from a gun. The speed of the bullet will be about the same as the speed of the recoiling gun

if the mass of the bullet equals the mass of the gun

The difference between impulse and impact force involves the ...

impact force x time, time is involved

Compared to the force that brings a small car to a stop, the force required to bring a heavy truck to a stop

impossible to determine without additional information

Padded dashboards in cars are safer in an accident than nonpadded ones because an occupant hitting the dash has

increased time of impac

When bullets are fired from an airplane in the forward direction, will the momentum of the airplane be affected? if so how and why?

it will decrease b/c of the bullets put on the plane.

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

An object that has kinetic energy must be

moving

A 1-N apple falls to the ground. The apple hits the ground with an impact force of about

not enough information

A large heavy truck and a small baby carriage roll down a hill. Neglecting friction, at the bottom of the hill, the baby carriage will have a greater

nothing. carriage is lighter

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

the same amount. it would stay the same.

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

the same as its potential energy

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

the target would be safer than the shooter

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

three times the usual power output

Strictly speaking, more gasoline is consumed by a running car if the air conditioner, headlights, or even the radio is turned on. Is this statement true? and If so, does it have anything to do with how fast the engine is turning?

true b/c the car has more work to do

If a certain object is raised twice as high, its potential energy will be...

twice as high

An object lifted 10 meters gains 200 J of potential energy. If the same object is lifted 20 meters its potential energy is

twice as much

If you push an object a given distance while applying twice as much force, you do how much work?

twice as much work.

If you push an object twice as far while applying the same force, how much work do you do?

twice as much work.

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

velocities

A large metal ball is shot from a cannon with a short barrel. Assuming the same amount of gunpowder is used, if the same ball were to be shot from cannon with a longer barrel, its muzzle velocity would be

more

An object at rest may also have

potential energy

Neglecting friction, a small ball and a similar large ball, both at rest, are allowed to roll down an incline for only one second. At this instant, the large ball will have a greater

potential energy

When a car is braked to a stop, its kinetic energy is transformed to what kind of energy?

potential energy b/c it is stopped

A job is done slowly, while an identical job must be 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

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

the bottom

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