Work, Power, and Efficiency

You are pushing a car as hard as you can for 5 minutes, but cannot get it to move.  How much work have you done on the car?

• There is not enough information to calculate the work.
• If you used 20 newtons of force, you will have done 100 Joules of work
• None. There was no movement.
• None of the answers are correct.

Find the work of a turtle that has a force of 27 newtons and travels a distance of 3 meters.

• 81 watts
• 81 joules
• 9 watts
• 9 joules

A bird used 8 watts of power and flew for 5 seconds.  How much work did the bird do?

• 40 watts
• 40 joules
• 1.6 watts
• 1.6 joules

How much power is needed to do 648 Joules of work in 100 seconds?

• 64800 Joules
• 64800 watts
• 6.48 watts
• 0.15 watts

How long does it take to do 432 joules of work with 75 watts of power?

• .17 seconds
• 5.76 seconds
• 5.76 meters
• 32400 seconds

measures the ratio of work output to work input

• joules
• power
• work
• efficiency

What is the efficiency of a machine if 55.3 J of work are done on the machine, but only 14.3 J or work are done by the machine?

• 0.25 Joules
• 26%
• 3.86 Joules
• 386%

How are work and and power related?

• if work is increased than the power generated is decreased
• there is not enough information given to know the answer
• if work is increased than power is increased
• work and power are not related

What units are used to measure power?

• watts
• Joules
• meters
• newtons

What units are used to measure work?

• Meter
• Watts
• Newtons
• Joules