# Physics

a motor lifts a 12 kg mass to a height of 15 meters at a content velocity in 3.5 seconds.
a) find the power
b) if the motor is only 35% efficient find the input energy

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1. change in potential energy = m g h = 12 * 9.81 * 15 = 1766 Joules
power = joules per second = 1766/3.5 =505 Watts

Input power = 505/.15 = 3363 Watts
Input energy = 3363 Watts * 15 seconds = 50,451 Joules

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posted by Damon

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