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### 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.

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

power

### 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

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

twice as much work

### 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

### 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

### 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

### 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 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with the respect to the ground?

80 J

### Two identical arrows, one with twice the kinetic energy of the other, are fired into a hay bale. The faster arrow will penetrate...

twice as far as the slower arrow

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

10%

### 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?

180 m

### 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

### 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

### Two identical arrows, one with twice the speed of the other, are fired into a hay bale. The faster arrow will penetrate...

four times further than the slower arrow