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« B          Main » Mechanical Energy » Power » LessonII_2_1   ### Power - Lesson II.2.1

 Key Terms: Power (P) | Horsepower | 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 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). • 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:   • 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:           