Question
Question: A small positively charged ball of mass m is suspended by an insulating thread of negligible mass. A...
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?
A
mgh
B
2 mgh
C
3 mgh
D
4 mgh
Answer
3 mgh
Explanation
Solution
dF = 
dFx = dF cos q
and Fx = 