JEE Main201912 Apr 2019Evening ShiftPhysicsMechanical Properties of FluidsActual
A solid sphere, of radius R acquires a terminal velocity v 1 when falling (due to gravity) through a viscous fluid having a coefficient of viscosity η . The sphere is broken into 27 identical solid spheres. If each of these spheres acquires a terminal velocity, v 2 , when falling through the same fluid, the ratio v 1 v 2 equals:
Options
- A1 9
- B27
- C1 27
- D9
Correct answer
D. 9
Step-by-step solution
If R is the radius of initial drop and r is the radius of new drop, then 4 3 π R 3 = 27 × 4 3 π r 3 ⇒ r = R 3 Terminal velocity, v T ∝ r 2 ⇒   v 1 v 2 = R 2 R 3 2 = 9