Question

A 10cmx10cmx10cm cube of density 650 kg / (m ^ 3) and is submerged in a container filled with water of density 1000 kg / (m ^ 3) . It is initially held at rest by a string which is attached to the bottom of the container, as shown in the figure. When we cut the string, the cube starts moving upwards. Find the initial acceleration of the cube, immediately after it is released. Answer in units of m/s^ 2

Answer 1

Mass of cube = 650*10^-3 = 0.65 kg

Buoyant force = m*g*d(fluid) /d(object)

Fb = 0.65*9.8*1000/650

Fb = 9.8 N

Weight of body = m*g

W = 0.65*9.8

W = 6.37 N

Net force, F = m*a

F = Fb - W

So, Equate both,

0.65*a = 9.8 - 6.37

a = 5.27 m/s^2

This will be the cube's acceleration.