The mass of a marble slab is 120 kg. What force must be applied to keep it under water?

Given:

m = 120 kilograms is the mass of the marble slab;

ro = 2700 kg / m3 (kilogram per cubic meter) – density of marble;

ro1 = 1000 kg / m3 – water density.

It is required to determine F (Newton) – what force must be applied to keep the marble slab under water.

Let’s find the volume that the marble slab occupies:

V = m / ro = 120/2700 = 0.044 m3 (the result has been rounded to one thousandth).

Then, according to Newton’s first law, we get:

F = F gravity – Farchimedes;

F = m * g – V * ro1 * g, where g = 10 Newton / kilogram (approximate value);

F = g * (m – V * ro1);

F = 10 * (120 – 0.044 * 1000) = 10 * (120 – 44) = 10 * 76 = 760 Newtons.

Answer: To keep the marble slab under water, you need to apply a force equal to 760 Newton.