Physics: Force, Vectors, and Free-Body Diagrams

Force

A push or pull on an object.

Vector Quantity

A quantity that has both magnitude and direction.

Newton (N)

Unit of force; 1 N = kg × m s-2.

Gravitational Force (Fg)

The force of attraction between objects due to their mass.

Electrostatic Force (FE)

The force of attraction or repulsion between objects due to their charge.

Contact Force

The force between two touching objects.

Applied Force (FA)

The force exerted when one object makes contact with another to push or pull it.

Tension Force (FT)

Pulling force of a rope or string on an object.

Normal Force (FN)

Force perpendicular to the surface upon which an object contacts.

Friction Force (Ff)

Force that opposes the sliding of two objects across one another.

Free-Body Diagrams

Diagrams used to show the relative magnitude and direction of all forces acting upon an object.

Net Force

The vector sum of all the forces acting on an object.

Equilibrium

When all forces cancel out, the object is in equilibrium.

Unbalanced Forces

Forces that cause accelerations.

Air Resistance Force

The force that opposes the motion of an object through air.

Spring Force

The force exerted by a compressed or stretched spring.

Weight Force

The gravitational force acting on an object, often referred to as weight.

Magnitude of Force

The size of the arrow in a free-body diagram reflects the magnitude of the force.

Direction of Force

The direction that the force is acting, indicated by the direction of the arrow in a free-body diagram.

Constant Velocity

No acceleration does not mean the object is not moving; it can still be moving at a constant velocity.

Practice Problems

Problems designed to apply concepts of forces and free-body diagrams.