Newton's First Law

rest, motion, constant, external force

"An object at rest remains at ____, and an object in motion continues in ____ at a ____ velocity unless acted upon by a net _____."

Inertia

• The tendency of an object to resist changes in its state of motion. The greater the mass, the greater this is.

Equillibrium

A state where the net external force acting on a body is zero. Here, an object at rest remains at rest, and an object in motion continues with constant velocity.

Contact Forces

Forces that arise from physical contact between two objects.

Normal Force

Contact force. The force exerted by a surface perpendicular to the object in contact with it.

Frictional Force

Contact force. The force resisting the relative motion or tendency of such motion of two surfaces in contact.

Non-Contact Force

Forces that act on an object without physical contact.

Gravitational Force

Non-Contact force. The attractive force between two masses, such as the Earth and an object.

Electromagnetic Force

Non-Contact force. Forces due to electric charges and magnetic fields.

Static Friction

The frictional force that resists the initiation of sliding motion between two surfaces.

Kinetic Friction

The frictional force acting between moving surfaces.

constant

Kinetic friction is generally _____ for a given pair of surfaces, regardless of the speed of motion.

opposes

Kinetic friction ____ the direction of relative motion between surfaces.