Given below are two statements: one is labelled as Assertion (A)...

Assertion (A) is correct. The initial acceleration of a sphere dropped in a viscous liquid is determined by the net force at $t=0$, where velocity and viscous drag are zero. The acceleration is $a = \dfrac{mg - F_b}{m} = g\left(1 - \dfrac{\sigma}{\rho}\right)$, where $\rho$ is the density of the material and $\sigma$ is the density of the liquid. This expression is independent of the radius of the sphere.

Reason (R) is incorrect. According to Stokes' law, the terminal velocity is given by $v_t = \dfrac{2r^2(\rho - \sigma)g}{9\eta}$. Thus, terminal velocity is directly proportional to the square of the radius ($v_t \propto r^2$) and is not independent of it.

Answer: (A) is correct but (R) is not correct