IB Physics A.2.1 Newton's Laws of Motion Key Definitions

Contact forces are forces that arise due to direct physical interaction between two objects.

Inertia is the tendency of an object to resist changes in its state of motion.

Newton’s first law of motion states:

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.

Newton's second law of motion states:

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

Newton’s third law of motion states:

For every action, there is an equal and opposite reaction.