Force

A push or pull exerted on an object.

Free-Body Diagram

A type of physical model used to represent the forces acting on a system.

Net Force

The vector sum of all the forces on an object.

Newton's Second Law

The observation that the acceleration of an object is proportional to the net force and inversely proportional to the mass of the object being accelerated.

Inertia

The tendency of an object to resist change.

Equilibrium

If the net force on an object is zero, then the object is in this state.

Apparent Weight

The force an object experiences as a result of all of the forces acting on it, giving the object an acceleration.

Weightlessness

When there are no contact forces pushing up on an object, and the object's apparent weight is zero.

Drag Force

The force exerted by a fluid on the object moving through the fluid. It is dependent on the motion of the object, the properties of the object, and the properties of the fluid that the object is moving through.

Terminal Velocity

The constant velocity that is reached when the drag force equals the force of gravity.

Interaction Pair

Two forces that are in opposite directions and have equal magnitude. (Also called an action-reaction pair of forces)

Newton's Third Law

This states that all forces come in pairs.

Tension

A specific name for the force exerted by a string or rope.

Normal Force

The perpendicular contact force exerted by a surface on another object.

Newton's Second Law Equation

A=F/M, or F=MA

The acceleration of an object is equal to the sum of the forces acting on the object, divided by the mass of the object.

The acceleration of an object is equal to the sum of the forces acting on the object, divided by the mass of the object.

Newton's First Law

The statement:

"An object that is at rest will remain at rest, and an object that is moving will continue to move in a straight line with constant speed, if and only if the net force acting on that object is zero."

Also called the "Law of Inertia"

"An object that is at rest will remain at rest, and an object that is moving will continue to move in a straight line with constant speed, if and only if the net force acting on that object is zero."

Also called the "Law of Inertia"

Newton's Third Law Equation

F = -F

A on B B on A

The force of A on B is equal in magnitude and opposite in direction of the force of B on A.

A on B B on A

The force of A on B is equal in magnitude and opposite in direction of the force of B on A.