Physics Chapter 7

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

twice as much work

A machine puts out 100 Watts of power for every 1000 Watts put into it. The efficiency of the machine is A) 10%. B) 50%. C) 90%. D) 110%. E) none of these

A

An object that has kinetic energy must be A) moving. B) falling. C) at an elevated position. D) at rest. E) none of these

A

Neglecting air resistance, a man on a high ladder releases a ball which strikes the ground with 100 J of kinetic energy. If he were to throw it straight upward instead, it will eventually reach the ground with a kinetic energy of A) 100 J. B) more than 100 J. C) less than 100 J.

A

A car that travels twice as fast as another when braking to a stop will skid A) twice as far. B) four times as far. C) depends on the mass of the cars

B

Two identical arrows, one with twice the kinetic energy of the other, are fired into a hay bale. The faster arrow will penetrate A) the same distance as the slower arrow. B) twice as far as the slower arrow. C) four times as far as the slower arrow. D) more than four times as far as the slower arrow. E) none of these

B

Which has greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60 km/hr? A) the 30 km/hr car B) the 60 km/hr car C) Both have the same kinetic energy. D) More information is needed about the distance traveled.

B

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 A) less than 40 J. B) more than 40 J. C) 40 J. D) impossible to predict without additional information

C

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 A) 10%. B) 20%. C) 50%. D) 80%. E) Not enough information is given.

C

After rolling halfway down an incline, a marble's kinetic energy is A) less than its potential energy. B) greater than its potential energy. C) the same as its potential energy. D) impossible to determine.

C

Two identical arrows, one with twice the speed of the other, are fired into a hay bale. The faster arrow will penetrate A) the same distance as the slower arrow. B) two times further than the slower arrow. C) four times further than the slower arrow. D) more than four times further than the slower arrow. E) none of these

C

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 A) 10 J. B) 500 J. C) 510 J. D) 5000 J. E) more than 5000 J.

D

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

An object may have potential energy because of its-

Location

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

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

The ball rolling down an incline has its maximum potential energy at-

The top

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

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 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 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

A 2 kg mass has 40 J of potential energy with respect to the ground. Approximately how high is it above the ground? A) 1 m B) 2 m C) 3 m D) 4 m E) none of these

B

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

1 W

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

A ball rolling down an incline has its minimum speed A) at the end the incline. B) half way down the incline. C) near the top of the incline. D) impossible to predict without knowing the ball's mass E) impossible to predict without knowing the size of the ball

C

A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with respect to the ground? A) 6 J B) 8 J C) 32 J D) 80 J E) none of these

D

A ball rolling down an incline has its maximum kinetic energy at A) the top. B) halfway down. C) three-quarters of the way down. D) the bottom.

D

A car moves 4 times as fast as another identical car. Compared to the slower car, the faster car has A) 4 times the KE. B) 8 times the KE. C) 12 times the KE. D) 16 times the KE.

D

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 150 km/hr? A) 20 m B) 60 m C) 90 m D) 120 m E) 180 m

E

Consider a hydraulic press. When the input piston is depressed 20 cm, the output piston is raised 1 cm. On the same press, an input force of 1 N can lift a load of A) 1 N. B) 10 N. C) 15 N. D) 20 N. E) All of the above are correct

E

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

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

2 W

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

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 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 A) less than 100 J. B) more than 100 J. C) 100 J. D) not enough information given

A