The Net Force is the sum of all forces acting on an object.

Forces must be treated as vectors when added! The net force vector and the acceleration vector are always in the same direction.

Force is proportional to the product of mass and acceleration.  If mass is constant then when acceleration is doubled then force is doubled! 

Law 2: Net Force = ma

The unit of force is the Newton!

Sir Issac Newton 1642- 1727

If one object exerts a force on a second object, then the second object exerts an equal force on the first object but in the exact opposite direction .

Mass is the measure of an object's inertia!  Inertia is a property of mass.  Inertia is NOT a force!

In the absence of a net external force an object will continue in its state of uniform motion. 

Newton correctly restated and revised a premise originated by Aristotle.  He recognized that inertial motion was straight line motion. 

Special Forces

Law of Universal Gravitation

Law 1: Inertia

An apple weights about one Newton!

LAW 1

LAW 2

LAW 3

links

Law 3: Action/Reaction Forces

May the Net Force be with you!

All forces come in pairs. Another way to think this is that an object cannot push on another object without being pushed back equally! 

The pair of forces never act on the same object so they never cancel each other!

The Concept of Force