Momentum and CollisionHard
Question
A tiny spherical oil drop carrying a net charge q is balanced in still air with a vertical uniform electric field of strength 
× 105 Vm-1. When the field is switched off, the drop is observed to fall with terminal velocity 2 × 10-3 ms-1. Given g = 9.8 ms-2, viscosity of the air = 1.8 × 10-5 Ns m-2 and the density of oil = 900 kg m-3, the magnitude of q is
× 105 Vm-1. When the field is switched off, the drop is observed to fall with terminal velocity 2 × 10-3 ms-1. Given g = 9.8 ms-2, viscosity of the air = 1.8 × 10-5 Ns m-2 and the density of oil = 900 kg m-3, the magnitude of q isOptions
A.1.6 × 10-19 C
B.3.2 × 10-19 C
C.4.8 × 10-19 C
D.8.0 × 10-19 C
Solution
πR3 ρg = qE = 6πηRvT∴ q = 8.0 × 10-19 C
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