Ch 08 Work and Power SAMPLE PROBLEMS
Multiple Choice
Identify the choice that best completes the statement or answers the question.
1.If a machine’s maximum power rating is 2,000 watts, what is the fastest time for it to do 1,000 joules of work?
2.If you do 500 joules of work using a force of 50 newtons, over what distance was the work accomplished?
3.Jasmine, who weighs 400 newtons, moves up a 5.0-meter climbing wall in 15 seconds. The amount of power generated by Jasmine as she climbs the wall is about ____ watts.
4.An electric food processor uses 250 joules of electrical energy every second. Due to friction and other causes, the energy available to spin the blades to cut food is reduced to 200 joules per second. The efficiency of the food processor is:
5.If a 75-percent efficient machine produces 7,500 joules of output work, what is the machine’s maximum input work?
6.An electrical water heater raises the temperature of water by adding 8,000 joules of energy to the water in 40 seconds. What is the minimum power required by the water heater?
7.The work output is 500 joules for a machine that is 25 percent efficient. The work output is ____ joules.
8.If a machine’s maximum power rating is 2,000 watts, how much work could it do in 40 seconds?
9.Robert lifts a 150-newton bucket of water 0.5 meters in 3 seconds. What is the amount of work done on the bucket?
10.As fuel burns in a jet engine, it releases 40,000 joules of energy. Out of this, only 16,000 joules are available to do work. The efficiency of the engine is ____ percent.
11.Jordan lifts a 100-kilogram barbell from the floor to a height of 2.0 meters in 1.5 seconds. The amount of power he generates is about ____ watts.
12.How much power is necessary to do 50 joules of work in 5 seconds?
13.An incandescent light bulb uses 60 joules of electrical energy every second. Due to heat loss, the energy available for light is reduced to only 6 joules per second. If this bulb is used to keep eggs warm in an incubator, about how efficient is the light bulb at producing HEAT?
14.A machine does 20,000 joules of work in 50 seconds. What is its power in watts?
15.Calculate the work needed to push a block with 4 newtons of force a distance of 10 meters.
16.An automobile engine exerts a force of 500 newtons on a car to travel 4,000 meters. What is the amount of work done by the engine?
17.A 2.2-kilogram crate is pulled by a 30-newton force over a distance of 5 meters. How many joules of work are done by pulling the crate?
18.Running up a flight of stairs, Marita generates 450 watts of power. If it takes her 6 seconds to go up the stairs, the amount of work she does in running up the stairs is ____ joules.
19.The efficiency of a modern bicycle is 95 percent. If you exert 200 joules in pedaling a bicycle on level ground, what is the work output?
20.A bowler lifts her bowling ball a distance of 0.5 meters using 35 joules of energy. If, on Earth, a 1.0 kilogram mass