An object weighs 20 N in air and 16 N in liquid then answer the following questions. i) What is the upthrust of the liquid on the object? ii)What is the weight of the displaced liquid? Write with reason.

Weight of the object in air, W(air) = 20N
Weight of the object in liquid, W(liquid) = 16N
Change in weight of the object, dW = W(air) - W(liquid) = 20N - 16N = 4N

(i)  Upthrust of the liquid on the object, U = dW = 4N

(ii) Weight of the displaced liquid =  Upthrust of the liquid on the object, U = 4N 

           Archimedes' principle states:-

Upthrust = Weight of the displaced liquid.