Question

A spherical body of mass m and radius r is allowed to fall in a medium of viscosity η. The time in which the velocity of the body increases from zero to 0.63 times the terminal velocity (v) is called time constant τ. Dimensionally τ can be represented by(a) $\frac{mr^{2}}{6\pi\eta}$(b) $\sqrt{[\frac{6\pi mr \eta}{g^{2}}]}$(c) $\frac{m}{6\pi\eta r v}$(d) None of these

Answer 1

Answer:d) is the answer

Do dimensional analysis