Power is an important concept in physics and is defined as the rate of doing wor

Question

Power is an important concept in physics and is defined as the rate of doing work – the work done divided by time. Its units are Watts (J/s). For example, a car may be able to expend the energy required to reach the top of a hill, but the cars horse power will determine how fast the car reaches the top of the hill. A 100 kg man is walking up a hill whose incline is 20o to the horizontal at a speed of 2.1 m/s. What power are they expending just raising their mass up the hill? Note in reality we are not efficient (which is why we generate heat as we work) and the power consumption would be expected to be around four times as large as your answer.

Explanation / Answer

Power = Force* velocity

force acting along the slope = mg sin a

where a = angle of the incline

P = mg sin a * v

P = 100*9.8*sin 20 *2.1

P = 703.87 W

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