Electric field strength	Gravitational field strength
The force exerted on each other, by two charged particles of charge Q1 and Q2, seperated by a distance r , is given by Coulombs law .	The gravitational force exerted on each by two point masses of mass m1 and m2 separated by a distance r is given by Newtons law of universal gravitation.
F = 1/ 4 π ε . m1 m2 / r2	F =G m1 m2 / r2

Notes:

• G is the universal gravitational constant and is equal to about 6.67 * 10^-11 N m² kg^-2.
• The costant ¹/ _{4 π ε} is used as ε is definde elsewhere.
• ε is the relative permittivity of the material in between the charges.