|MadSci Network: Physics|
Naturally, the difficulty lies in the definition of the power of the motor. Is it the power that it draws from the wall, or is it the power that it is capable of delivering? I have little experience with motors, but I can make some qualified guesses. Comparing with radio frequency transmitters, if the box says it delivers 1000 Watts, then I expect to get 1000 Watts of output from that transmitter. I am certain that it draws much more than that out of the wall because the box has to have large fans to keep it cool. Some of the energy coming from the wall is converted to heat, and is lost. Given that comparison, I would expect that the 5hp motor gives 5hp as its output, and that the shorter time is correct. If you feel the need for another example, you might consider an automobile engine. The horsepower rating of an engine is not very meaningful if it refers to the power consumption. There is a much better rating for that quality (MPG). I would assume that the horsepower refers to the power output of that engine.
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