Q 11-09-002NEETNEET 2026Top questionMedium
In the measurement of viscosity of liquids using terminal velocity experiment, spherical balls of same radius but having different densities are used. The variation of the terminal velocity ($v$) with the ratio of density of spherical ball ($\sigma$) to density of the liquid ($\rho$), is best represented by :
Answer: (A) see figure
Concept. Stokes' terminal velocity: $v = \dfrac{2r^2(\sigma - \rho)g}{9\eta}$.
Step 1. In terms of $\dfrac{\sigma}{\rho}$.
$$v = \frac{2r^2\rho g}{9\eta}\left(\frac{\sigma}{\rho} - 1\right)$$
Step 2. Shape. A straight line, zero at $\dfrac{\sigma}{\rho} = 1$ and rising beyond it (lighter balls do not sink): graph (1).
Answer. Graph (1) (Option A).
Solution by Sreeraj P, M.Sc Physics