Friction
- Symbol: F(f)
- Definition: The contact force that acts to oppose sliding motion between surfaces
- Direction: Parallel to the surface and opposite to the direction of sliding
Normal
- Symbol: F(N)
- Definition: The contact force exerted by a surface on an object
- Direction: Perpendicular to and away from the surface
Spring
- Symbol: F(sp)
- Definition: A restoring force; that is, the push or pull a spring exerts on an object
- Direction: Opposite the displacement of the object at the end of the spring
Tension
- Symbol: F(T)
- Definition: The pull exerted by a string, rope, or cable when attached to a body and pulled taut
- Direction: Away from the object and parallel to the string, rope, or cable at the point of attachment
Thrust
- Symbol: F(thrust)
- Definition: A general term for the forces that move objects such as rockets, planes, cars, and people
- Direction: In the same direction as the acceleration of the object, barring any resistive forces
Weight
- Symbol: F(g)
- Definition: A field force due to gravitational attraction between 2 objects, generally Earth and an object
- Directional: Straight down toward the center of the Earth