Forces acting on an object

Friction - is a force created when 2 materials slide against each other. It occurs in an opposite direction to motion.

Smooth Surface - there is no frictional force

Weight - the force created by a mass being pulled downwards due to gravity. W=mg

Normal Reaction - the force created by a surface pushing back against an object. It acts perpendicular to the surface.

Static - an object does not move

Light - mass can be ignored

Tension - the force of a string on an object

Particle - the object has no mass or size so are treated as a single point

String - has no thickness and is not elastic

Rough Surface - friction will cat in the opposite direction to motion

Rigid - a rod will not bend. If two objects pull away from each other then it can act with a force due to tension. If two objects push towards each other then the rod can act with thrust.

Newton's 2nd Law of motion

Example

Newtons 1st Law of motion

Newton's 3rd Law of motion

An object is in equilibrium if it is static or if it has a constant velocity (no acceleration)

An object will remain in equilibrium unless a force acts on it

Example

The acceleration acting on an object is related to the mass of the object and the total force acting on it. F=ma

Any two bodies in contact exert an equal but opposite force on each other

Smooth Pulleys and Connected Particles

Example