Question

An 80 kg man climbs a 50 m-high hill in 20 minutes. What is the average power in watts he expends climbing the hill?

Answer 1

Question#19151

An 80 kg man climbs a 50 m-high hill in 20 minutes. What is the average power in watts he expends climbing the hill?

Solution:

Let:

$$m = 50 \text{ kg}$$ $$H = 50 \text{ m}$$ $$t = 20 \text{ min} = 1200 \text{ sec}$$

W-?

$\mathbf{W} = \frac{\mathbf{A}}{t}$, were A- the done work

Such as the done work is equal to change a potential energy:

$$A = \Delta E_p = mgH, \text{ g} = 9,8 \text{ m/s}^2$$ $$\mathbf{W} = \frac{mgH}{t}$$ $$\mathbf{W} = \frac{50 \times 9.8 \times 50}{1200} = 20.42 \text{ watt}$$

Answer: 20,42 watt.