99 Percentile Qs Bank for JEE MainPhysicsWork, Power and Energy
A small positively charged ball of mass m is suspended by an insulating thread of negligible mass. Another positively charged small ball is moved very slowly from a large distance until it is in the original position of the first ball. As a result, the first ball rises by h . How much work has been done?
Options
- A2 m g h
- B3 m g h
- C4 m g h
- D5 m g h
Correct answer
B. 3 m g h
Step-by-step solution
m g F = I x ;   F = K q Q x 2 x 2 ; I = h : x X = k q Q 2 m g 2 ,   E electrostatic = k q Q x = 2 m g h ∴ W = 2 m g h + m g h = 3 m g h