When the moon faces earth a solar eclipse happens :-)
The hardest part of the job is to find the right formula to use, and write it down. You've already done that ! The rest is just turning the crank until an answer falls out.
You wrote. E = m g h.
Beautiful.
Now divide each side by (g h), and you'll have the formula for mass:
m = E / (g h).
You know all the numbers on the right side. Just pluggum in, do the arithmetic, and you'll have the mass.
The answer is the first one
To solve this problem we will apply the concepts related to Coulomb's law for which the Electrostatic Force is defined as,
Here,
k = Coulomb's constant
= Charge at each object
r = Distance between them
As the distance is doubled so,
Therefore the factor is 1/4
