Determine the volume of the body if it is known that in water its weight is 80N, and in water it is 100N.

Given:

P1 = 100 Newton – body weight in air;

P2 = 80 Newton – body weight in water;

g = 10 m / s ^ 2 – acceleration of gravity;

ro = 1000 kg / m ^ 3 is the density of water.

It is required to determine the volume of the body V (m ^ 3).

Newton’s second law for a body in water can be written as follows:

P1 – A = P2 where A is the buoyant (Archimedean) force acting on the body. Then:

P1 – ro * V * g = P2;

P1 – P2 = ro * V * g;

V = (P1 – P2) / (ro * g) = (100 – 80) / (1000 * 10) = 20/10000 = 0.002 m ^ 3.

Answer: the volume of the body is 0.002 m ^ 3 (2 liters).