Different types of forces

A list of some different types of forces that are encountered regularly in physics is shown below.

Normal force:

Definition: The normal force is the force exerted by a surface on an object.

Direction: Perpendicular to and away from the surface.

Symbol: F_N

Example: Put a book or a globe on a table. The table exerts a normal force on the book or the globe which prevents the book or the globe from falling down.

Frictional force:

Definition: The frictional force is the force that resists sliding motion between surfaces.

Direction: Parallel to the surface and opposite the direction of sliding.

Symbol: F_f

Example: You put a book on the floor and you kick it so it slides on the floor. The book will eventually stop sliding because of the force of friction.

Weight:

Definition: The weight is the force caused by the gravitational attraction between two objects. Generally this force happens between the earth and an object.

Direction: Straight down toward the center of the earth.

Symbol: F_g

Example: Every time you jump into the air, your weight is the force that keeps pulling you down. If you put a globe on a table, the weight is the force that pushes down on the table.

Tension:

Definition: The tension is the pull exerted by a rope, cable, or string when attached to an object and stretched tight.

Direction: Away from the object or the point of attachment and parallel to the rope, cable, or string.

Symbol: F_T