Power and Efficiency

Multiple Choice

Which of the following is TRUE?

• Machines put out MORE work than what is put in

• Machines make work harder.

• The total energy is conserved

• Work input is less than output

Open Ended

What type of energy is the "waste heat"?

Multiple Choice

What will be the unit for efficiency?

• Joules

• Percent

• Newtons

• Joules/sec

Multiple Choice

You see a newspaper advertisement for a new, highly efficient machine. The machine claims to produce 2,000 joules of output work for every 2,100 joules of input work.

What is the efficiency?

• 95%

• 100%

• 105%

• 10%

Multiple Choice

Which weightlifter has more power and WHY?

• Michael because his legs are stronger

• Jim because he lifted more weight.

• Michael because he lifted it in more time

• Jim because he lifted the weight in less time.

Multiple Select

What is the unit(s) for Power? (more than 1 may be correct)

• Joules

• Watts

• Joules/sec

• seconds

Multiple Choice

• Allen lifts his weight (500 newtons) up a staircase that is 5 meters high in 30 seconds. 

• How much power does he use?

• 83.3 Watts

• 16.6 watts

• 3.33 watts

• 3000 Watts

Multiple Choice

How does Allen's power compare to a 100 watt light bulb?

• His power is greater

• His power is less

• His power is equal to a light bulb

• Power by a person can not be compared to a light bulb