Question 12

A boy, of mass 50 kg, runs up a staircase of 45 steps in 10 s. If the height of each step is 14 cm, find his power. Take g= $$10ms^{-2}$$

Solution

A boy, of mass 50 kg, runs up a staircase of 45 steps in 10 s. If the height of each step is 14 cm, so with each step his potential energy is increasing.

total height $$= 14\times 45 = 630$$

Potential energy at the top $$= m\times g\times h = 50\times10\times 630 = 3150 KJ$$

Power = $$\frac{Potential  energy}{Time}$$

$$=\frac{3150}{10} W = 315 W$$

Option B is correct.


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