Question

A boy weighing 350 N climbs up the 30 steps, each 20 cm high in 1 minute. Calculate:(i) the work is done, and (ii) the power spent.

Answer 1

Total distance covered in 30 steps , S= 30 $\times$ 20 cm = 600 cm = 6 m
Work done by the boy in climbing= Force $\times$ distance moved in direction of force

Here work done by boy will be opposite to work done by gravity.

Weight is basically a force exerted on our body due to gravity. Therefore boy will have to apply exact amount of force in opposite to gravity i.e. in upward direction. Work is:
(i) W= F$\times$ S= 350 $\times$ 6 =2100 J

(ii) Power is rate of doing work per second , therefore:
1 minute = 60 sec