Question

what is internal force, explain with examples
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Answer 1

Answer:

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.

Answer 2

Internal forces are forces transferred by the objects in the system.

Examples :- tension in a stretched elastic and the compression caused by the weight of a roof pressing down on the walls of a building.