Question

What is meant by external force and internal force?

Answer 1

External forces are those which have a capability to alter the total mechanical energy of an object.eg. Gravitational Force, Spring Force

Internal forces do not have the capability to alter the mechanical energy of the object but they can change the mechanical energy from one form to another, say potential energy to kinetic energy.eg. tension Force, Applied Force (Push or pull etc.)

I hope you've got your answer.