Question

What do you understand by external and internal force

Answer 1

Answer:

External forces are forces caused by external agent present outside of the system. External non-zero net force imparts an acceleration to the center of mass of the system regardless of point of application.

Internal forces are forces exchanged by the objects in the system. Internal forces may cause acceleration in different parts of the system but does not cause any acceleration in the center of mass of the entire system.

Example:

Friction is an external force if the body experiencing friction in the system.

If both the bodies involved in friction are considered as a system, then it acts as an internal force.

hope it helps you....