Category:Internal Forces

This category contains results about Internal Forces.
Definitions specific to this category can be found in Definitions/Internal Forces.

Let $B$ be a body.

An internal force is a force $\mathbf f$ exerted by one particle $P_1$ of $B$ on another particle $P_2$ of $B$, and to which there exists an equal and opposite reaction exerted by $P_2$ upon $P_1$.

Hence internal forces exist in pairs whose individual resultants are zero.

Hence the resultant of all the internal forces is also zero.