There are two types of forces depending on how it was applied: (1) external or (2) internal:
- External forces apply directly to the object.
- Internal forces act within the object.
For example, when you kick a ball, the force you apply is external. It's the reason why the ball moved from one place to another. In addition to this, the ball changes shape when you kick it. It may not be apparent, but every non-rigid object will deform. The reason why it did so is because of internal forces.
Summary
There are two types of forces: external and internal.
External forces apply directly to the object.
Internal forces act within the object.
