Question

A labourer lifts a bag of mass loo kg to a roof at height of 4m. Calculate the work done take
acceleration due to gravity as 10m/s​

Answer 1

Explanation:

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ANSWER

Apparent weight =mg−FB

where, FB is buoyant force and mg is weight

 We know that buoyant force FB will be:

FB=Vρwaterg=ρstonemρwaterg

where V is volume of stone =ρstonem and  ρwater is density of water

As specific gravity is given as 3 it's density will be three times of water

ρwaterρstone=3

Hence, FB=3mg

Putting the values of m,g and applying the formula for work done,

Work done = Apparent weight × displacement

                    =10×g×h−310×g×h

                    =32×10×10×6

                    =400 J