Question

Calculate the work done in raising a stone of mass 5kg and specific gravity 3, lying at the bed of a lake through a hight of 4m.

Ans=130.7 J

Answer 1

Loss of weight in water = weight in air / specific gravity = 5/3

Weight of stone in water = 5-5/3 = 10/3

Force = 10/3 x 9.8 = 98/3

Work done = 4 x 98/3 = 130.666 => 130.7(appx)J

Answer 2

Loss of weight in water = weight in air

/ specific gravity

= 5/3

Weight of stone in water = 5 - 5/3

= 10/3

Force = 10/3 × 9.8

= 98/3

Work done = 4 × 98/3

= 130.7 J ( approximately)