Question

A particle of mass M and charge Q is attached to a string of length L. It is whirled into a vertical circle in field E. The speed of the particle at point A, so that the tension in the string at A is ten times the weight of particle, is - (g = acceleration due to gravity)

• A. $\sqrt{5gL}$
• B. $\left( \frac{QE}{M}L \right)^{1/2}$
• C. $\sqrt{L\left( 9g + \frac{QE}{m} \right)}$
• D. None of the

Answer 1

Answer: (C)

$\sqrt{L\left( 9g + \frac{QE}{m} \right)}$

Answer 2

(T + QE) – mg =

10 mg + QE – mg =

9 mg + $\frac { \mathrm { QE } } { \mathrm { m } } = \frac { \mathrm { mv } ^ { 2 } } { \mathrm {~L} }$ , v =