An object maintains its state of motion unless acted upon by a net external force.

The tendency of an object to resist changes in its state of motion.

A state where the net force on an object is zero, resulting in constant velocity.

A reference frame in which Newton's First Law holds true; an object with no net force maintains constant velocity.

The vector sum of all forces acting on an object.

An object at rest stays at rest, and an object in motion stays in motion with the same velocity, unless a net force acts on it.

Inertia is an object's resistance to change in its state of motion.

Translational equilibrium occurs when the vector sum of all forces acting on an object equals zero, resulting in no net force and no acceleration.

Static equilibrium is when an object is at rest and the net force acting on it is zero.

Dynamic equilibrium is when an object is moving at a constant velocity and the net force acting on it is zero.

An inertial reference frame is one in which Newton's first law holds true; it is a non-accelerating frame.

Balanced forces: Sum to zero, maintain translational equilibrium, no change in velocity. | Unbalanced forces: Result in a non-zero net force, cause acceleration.

Static equilibrium: Object is at rest, net force is zero. | Dynamic equilibrium: Object is moving at constant velocity, net force is zero.

Inertial reference frame: Newton's first law holds true, non-accelerating. | Non-inertial reference frame: Accelerating, Newton's first law may not directly apply (fictitious forces may be needed).