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14.6
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14.6: Work & Power
What is Work?

Work is the product of force and distance, or:
Work = Force x Distance

Work is measured in Newton-meters (N x m), which are called joules (J).
What is Power?
Power is the rate of doing work. Doing work at a faster rate requires more power. With more
power, you can do more work in the same time or do the same amount of work in less time. For
example, if you use a snowblower instead of a shovel, you can move more snow in the same
amount of time, or you can move the same amount of snow in a shorter time. This is because the
snowblower has more power.
Calculating Power:
To calculate power, you divide the amount of work done by the time needed to do the work. The
equation for power is:
Power = Work
Time
W
P
t
Time is measured in seconds(s). The unit of power is the watt (W). A watt equals one joule per
second. For example, an 800 watt microwave uses 800 joules of power in one second.
Another common unit of power is the horsepower (hp). One horsepower equals about 747 watts.
The horsepower of a lawnmower might by 4 hp, whereas the horsepower of a car might be 190
hp, or almost 142,000 watts of power.
Name
_________________________
Block ________________ PSA
West
1. A light bulb does 100 joules of work in 2.5 seconds. How
much
power
does it have?
Date
Due
_______________
14.6
Givens & unknown
Formula used
Plug #’s into formula
Answer (No naked #’s)
2. A man exerts 700 newtons of force to move a piece of furniture 4 meters. If it takes him 2
seconds to move the furniture, how much power does it require?
Givens & unknown
Formula used
Plug #’s into formula
Answer (No naked #’s)
3. A hair curling iron uses 13 watts of power. How long must it operate to do 1,040 joules of
work?
Givens & unknown
Formula used
Plug #’s into formula
Answer (No naked #’s)
4. A 4 watt night light is left on for 8 hours each night. How much work does it do per night?
Givens & unknown
Formula used
Plug #’s into formula
Answer (No naked #’s)
5. How much horsepower is needed to move a box that has a force of 1,492 newtons a distance
of 2 meters in 1 second?
Givens & unknown
Formula used
Plug #’s into formula
Answer (No naked #’s)