Newton's Laws of Motion and Related Concepts

Law of Inertia (First Law)

A body remains at rest or moves at constant velocity unless acted upon by a net external force.

Law of Acceleration (Second Law)

Acceleration occurs when a net external force acts on a body. The direction of acceleration is the same as the net force.

Law of Interaction

For every action, there is an equal and opposite reaction. When two bodies interact, the forces they exert on each other are equal in magnitude and opposite in direction.

Inertial Frame

Is one where an object remains at rest or moves at constant velocity unless a force acts on it.

Force

A push or pull resulting from interactions between objects (Newtons).

Contact Force

Force that involves physical contact.

Normal Force

Perpendicular to the contact surface.

Tension Force

Pulling force in strings, ropes, or cables.

Friction Force

Opposes motion between surfaces.

Kinetic Friction

Acts on moving objects.

Static Friction

Prevents motion; must be overcome to initiate movement.

Noncontact Force

Force that acts at a distance.

Gravitation Force

Earth’s pull on objects.

Free Body Diagrams

Isolates and object and shows all forces acting on it, using vectors to represent magnitude and direction.