Question

A table -tennis ball is held under water and then released. Described and explain the subsequent motion of the ball

Answer 1

The mass of the ball is $2.7(g)$

The diameter of the ball is $40 (mm)$

Gravity, buoyant force and the resistance force of the medium act on the ball.

$F_G=mg=0.0027\cdot(-9.8)\approx-0.03(N)$

$F_B=\rho gV=1000\cdot9.8\cdot(4/3)\cdot\pi\cdot0.02^3\approx0.34(N)$

$F_R=-kv$.

So, if the force of gravity and the force of resistance of the medium become equal to the modulus of the buoyant force, the ball will move up at a constant speed.