The Coulomb force between two or more charged bodies is the force between them due to Coulomb's law. If the particles are both positively or negatively charged, the force is repulsive; if they are of opposite charge, it is attractive. ... Like the gravitational force, the Coulomb force is an inverse square law.
Angstrom = 10^-10 m
for nucleus size are used fermi (femtometer 10^-15 m )
Answer : Height, h = 20.4 m
Explanation :
It is given that,
Mass of an object, m = 500 g = 0.5 kg
Gravitational potential energy, PE = 100 J
The Gravitational potential energy is the energy which is possessed due to the height and gravity of an object. It is given as :
PE = m g h
where,
h is the height of the cliff.

h = 20.40 m
So, the height of the cliff is 20.4 m.
The centripetal acceleration is 
Explanation:
For an object in uniform circular motion, the centripetal acceleration is given by

where
v is the speed of the object
r is the radius of the circle
The speed of the object is equal to the ratio between the length of the circumference (
) and the period of revolution (T), so it can be rewritten as

Therefore we can rewrite the acceleration as

For the particle in this problem,
r = 2.06 cm = 0.0206 m
While it makes 4 revolutions each second, so the period is

Substituting into the equation, we find the acceleration:

Learn more about centripetal acceleration:
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