Contact and non-contact forces

• Contact forces are responsible for all the interactions between particles and objects, and can be divided into two categories: contact forces and non-contact forces.
• Contact forces include a push or a pull, and the unit of force is the newton (N).
• Examples of contact forces include reaction force, tension, and friction.
• Reaction force is an object at rest on a surface experiences, acting in the opposite direction to an action force.
• Tension is a pull exerted by each end of an object such as a string or rope.
• Friction is a force that opposes or prevents movement and converts kinetic energy into heat.
• When a contact force acts between two objects, both objects experience the same size force, but in opposite directions, this is Newton's Third Law of Motion.
• Non-contact forces include gravity, forces and elasticity, describing motion, forces, acceleration and Newton's laws, momentum, and air resistance.
• Gravity is a force that attracts all objects with mass towards each other.