Physics chatper 7

A 500 N barbell is lifted 2.2 m above the floor. What is the gain of potential energy of the barbell when it is lifted to this height? Express your answer to two significant figures

1100 J

Belly-flop Bernie dives from atop a tall flagpole into a swimming pool below. His potential energy at the top is 13000 J (relative to the surface of the pool). What is his kinetic energy when his potential energy reduces to 1000 J?

12,000 J

A How much work is done when you push a crate horizontally with 100 N across a 14-m factory floor? B If the force of friction on the crate is a steady 70 N, find the KE gained by the crate.

1400 J, 420 J

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

16 times the KE.

Do 100 J of work in 50 s and your power output is...

2 W

A 2500-N pile-driver ram falls 10 m and drives a post 0.1 m into the ground. The average impact force on the ram is

250,000 N

How many Joules of energy are in one kilowatt-hour?

3.6 million

A TV set is pushed a distance of 2 m with a force of 20 N. How much work is done on the set?

40 J

A bow is drawn so that it has 40 J of potential energy. When fired, the arrow will ideally have a kinetic energy that is...

40 J

Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed to do this job was

50 w

A diver who weighs 500 N steps off a diving board that is 10 m above the water. The diver hits the water with kinetic energy of

5000 J

A diver who weighs 500 N steps off a diving board that is 10 m above the water. The diver hits the water with kinetic energy of...

5000 J

Work = force × distance: W=Fd Calculate the work done when a 26-N force pushes a cart 3.5 m

91 J

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.

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

both requires the same amount of work

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

decreased

A car that travels twice as fast as another when braking to a stop will skid

four times as far.

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

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

An object that has kinetic energy must be...

moving

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 these

An object at rest may also have...

potential energy

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

power

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

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

A moving object has..

speed, velocity, momentum, and energy

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

the 60 km/hr

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

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 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

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

twice as much

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