A body weighs 160N in air and 120N when totally immersed in a liquid of relative density (R. D) 0.80. Calculate the relative density of the body.​

3.2

Explanation:

The computation of the relative density of the body is shown below:

Given that

W denotes the weight of the body in air = 160 N

ρ' denotes  density of the body

V denotes  volume of the body

Now weight of the body in the air is  

W = ρ' V g   (1)

And,

W' denotes weight of the body in liquid = 120 N

Now the force of buoyancy is

F = W - W'

= 160 - 120

= 40 N

And, ρ denotes density of liquid

The force of buoyancy is  

F = ρ V g (2)

Now divide equation 1 from equation 2

160 ÷ 40 =  ρ' V g  ÷ (ρ V g )

4 =  ρ'  ÷ (0.8 )

ρ' = 3.2

that would be because of both gravity and friction. so     c