Question

A boy takes 3 minutes to lift a 20 litre water bucket from a 20 m deep well, while his father does it in 2 minutes. (a) Compare:(i) the work, and (ii) How much work each does ? Take density of water = 10×10×10 kg / m×m×m and g =9.8 N/kg

Answer 1

Answer:

volume of water =201 =20/1000 =0.02 m^3

mass of water = density × volume = 10^3×0.02=20 kg

(I) work done by boy = mgh = 20 × 9.8×20 = 3920j

work done by father =mgh =20×9.8×20=3920j

compare work done :

3920:3920

1.1

(ii) time taken by boy = 3min =180s

time taken by father = 2 min =120s

power developed by the boy =work done /time =3920/180

power developed by father = work done/time =3920/120

comparing power developed :

3920/180:3920/120

=2.3