Internal force

Definition

Internal force is a force that acts between particles within a system, causing interactions but not changing the overall momentum of the system. These forces are responsible for maintaining the integrity and shape of the system.

5 Must Know Facts For Your Next Test

1. Internal forces do not contribute to changes in the total linear momentum of a system.
2. They can include gravitational, electromagnetic, and nuclear forces within the system.
3. According to Newton's Third Law, internal forces always occur in equal and opposite pairs.
4. In collisions, internal forces can cause deformation or change in kinetic energy within the interacting bodies.
5. The center of mass motion is unaffected by internal forces; it is only influenced by external forces.

Review Questions

• Why don't internal forces affect the total linear momentum of a system?
• How do internal forces adhere to Newton's Third Law?
• Can an internal force cause a change in the center of mass motion? Why or why not?

Related terms

External Force: A force acting on a system from outside its boundary, capable of changing the system's total momentum.

Center of Mass: The point representing the mean position of the matter in a body or system.

Newton's Third Law: $\text{For every action, there is an equal and opposite reaction}$. This law explains how internal forces come in pairs.