A force is a push or pull acting upon an object as a result of its interaction with another object.

Contact forces and non-contact forces.

Friction, tension, and normal force are examples of contact forces.

Gravity, magnetic force, and electrostatic force are examples of non-contact forces.

An object is in motion if its position changes relative to a reference point over time.

A force applied to an object can cause it to accelerate, change direction, or change shape, thus affecting its motion.

An object at rest stays at rest, and an object in motion stays in motion at a constant velocity unless acted upon by a net external force.