Question

Calculate the work done in raising a stone of mass 4kg of specific gravity 4, immersed in water from a depth of 3m to 1m below the surface

Answer 1

Answer:

48 J

Step by step explanation:

The givens are:

• Mass = 4 kg
• Gravitational force of acceleration = 4 $m/s^2$
• Displacement = 3 m

Work = Force * Displacement

Force = mass * acceleration

Therefore, F = 4*4 = 16 N

Therefore, work = 16*3 = 48 J

Answer 2

The net work done will be 58.8 Joules

Explanation :

Specific gravity or relative density is defined as ratio of density of the object to ratio of density of water

Hence , ρ/ρ₀ = 4

if V be the volume of the object, then according to Archimedes principle;

Net weight of the object = weight - buoyant force

= ρVg - ρ₀Vg

= ρVg(1- ρ₀/ρ)

=  4 x 9.8 x (1 - 1/4)                           [as ρV = mass of the object = 4 kg

= 4 x 9.8 x 3/4

= 29.4 N

Hence work done = weight x distance

= 29.4 x 2

= 58.8 Joules

Hence the net work done will be 58.8 Joules