Question

Coulomb's Law

1. What evidence do you see that Newton's third law applies to electrostatic forces?

2. Electric force is a force of attraction or repulsion between objects based on their charges and their distance apart.

(a) When is the electric force attractive?

(b) When is the electric force repulsive?

3. Explain how electric forces are like gravitation forces and how they differ.

Answer 1

1. if we take two charges Q1 and Q2 which are placed r distance  apart from each other, then, by Coulomb’s law, we can say -

Electrostatic force on Q1 by Q2 = electrostatic force on Q2 by Q1 = (K×Q1×Q2)/(r²)

and according to Newton's third law if object A exerts a force on object B, then object B also exerts an equal and opposite force on object A.

SO this shows that  electrostatic force follows Newton's third law of motion.

2

a).If the particles or both the charges  are different or alike for example one is positive then another one is negative , then the electric force is attractive force .(Different charges attract  each others).

b).If the particles or both the charges  are positively or negatively charged, then the electric force is repulsive  force .(like charges repel each others).

3.

The force equations are similar, so the behavior of interacting masses is similar to that of interacting charges.

like

- both have constants like electric force has constant K ( permittivity of free space ) and gravitation force has constant G( universal gravitation constant).

- both follows inverse square law means inversely proportional to the square of the separation distance between the object's centers. in the case of electric force objects are charges while in case of gravitation force objects are two masses.

differ

The main difference is that gravitational forces are always attractive, while electrostatic forces can be attractive or repulsive. Charge plays the same role for electrostatics that mass plays for gravity.