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Power (P)
To be a powerful lineman you should be strong (apply a large force) and quick (displacement occurs over a short period of time).
- Power is the rate at which work is done.
A Walker
-work done is large
-time is very large
-power rating would be small
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A Rock Climber
-work done is large
- it takes less time than the walker
- power rating would larger than the walker
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A Bicycler
- work done is large
- it takes less time than the walker and rock climber
- power rating is larger than the rock climber
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- The SI unit for power is the watt (W).
- A non-SI unit for power, which is still commonly used, is the horsepower.
1 horsepower = 746 watts
| Sample Problem
A student does 82 J of work when lifting her textbooks from the floor to her desk. It took her 3.0 s to do this task. What is her power?
Solution:
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- Since work done is approximately equal to the energy used, W = ~E,
power can also be described as the rate at which energy is used.
- To determine power produced by a moving object you must know its force and average velocity.
Reasoning:
Where:
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