Question

Two identical balls each have a mass of `10 g`. What charges should these balls be given so that their interaction equalizes the force of universal gravitaion acting between them? The radii of the balls may be ignored in comparison to distance between them.
A. `6.34xx10^(-11)C`
B. `8.57xx10^(-11)C`
C. `6.34xx10^(-13)C`
D. `8.57xx10^(-13)C`

Answer 1

Correct Answer - d
If `q` is charge given to each ball, then
`1/(4piepsilon_(0))*(qxxq)/(r^(2))=G(mxxm)/(r^(2))`
or `q=sqrt(4piepsilon_(0)G)xxm`
Setting `G= 6.6xx10^(-11) Nm^(2) kg^(-2)` and
`m=10 g=10xx10^(-3)kg`, we get
`q=8.57xx10^(-13)C`