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Power - Lesson II.2.1

Key Terms:

Power (P) | Horsepower | IL, CCT, NUM

Power (P)

Football Player
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.


Walker on hill
A Walker
-work done is large
-time is very large
-power rating would be small
Rock climber
A Rock Climber
-work done is large
- it takes less time than the walker
- power rating would larger than the walker
A Bicycler
- work done is large
- it takes less time than the walker and rock climber
- power rating is larger than the rock climber

  • The SI unit for power is the watt (W).

    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?


Check Point

  • 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.



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