Power

We hear the word power tossed around quite a bit, but not many people really understands what it means. We are told that what makes an athlete an extraordinary one, is not the fact that they can exert a great deal of force (and therefore they can do a great deal of work) but that they are strong and fast. In short these people can do a great deal of work in a quick amount of time. This means that they are powerful.

Power refers to how quickly one can do work. The quicker the work is done the more power that is needed.

If time to complete work remains costant, the more work done the more power there is
(work and power are directly proportional).
If work done remains constant, the shorter the time to complete the work the more power there is
(time to complete work and power are inversely proportional).


This leads to the following equation for power:
power = work / time where units will be joules/sec
1 joule/sec = 1 watt
746 watts = 1 Horse Power

Why do we talk about the horsepower of engines? Well the horsepower of an engine tells us how quickly it can do work. For instance, the motor that pulls rollercoaster cars up the first big hill and the engine on a typical automobile can produce the same amount of force over a distance. This means that both motors can do the same amount of work.

Does this mean that both motors have the same horsepower? ..... Definitely NOT!! Look below to see

Did you ever notice how long it takes to get up the first hill on a rollercoaster? The motor does its work very slowly this means it does not have much power. You would not want your car to do its work so slowly otherwise starting at a stop light would take as long as it takes the rollercoaster to get up the hill. Because your car can do its work much more quickly it has much more power.

Look Here for Practice Problems:     Problem Set #1      Problem Set #2

       
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