Question

Compare and contrast the electric force with the gravitational force

Answer 1

Similarities:

- The gravitational force and the electric force have a similar form.

In fact, gravitational force is given by:

$F=G\frac{m_1 m_2}{r^2}$

where G is the gravitational constant, m1 and m2 are the masses of the two objects, r is the separation between the two objects.

The electric force is given by:

$F=k\frac{q_1 q_2}{r^2}$

where k is the Coulomb constant, q1 and q2 are the charges of the two objects, r is the separation between the two objects.

As we see, the two forces have same dependency on the distance (inversely proportional to the square of the distance)

- Both forces are non-contact forces: this means that in both cases, the two objects do not to be in contact with each other, because the force is still acting from a distance also.

Differencies:

- The gravitational force is attractive only; on the contrary, the electric force can be either attractive or repulsive, depending on the relative sign of the two charges. In fact, when the two charges have same sign, the force is repulsive; when the two charges have opposite sign, the force is attractive.

- The gravitational force is much weaker than the electric force. This can be seen by comparing the value of the constant in the two formulas; we have:

$G=6.67\cdot 10^{-11} m^3 kg^{-1}s^{-2}$ for the gravitational force

$k=8.99 \cdot 10^9 Nm^2C^{-2}$ for the electric force

As we see, the electric force is much stronger than the gravitational force.