Normal force

Definition

The normal force is the perpendicular contact force exerted by a surface on an object in contact with it. It acts perpendicular to the surface and counteracts the component of other forces acting in that direction.

5 Must Know Facts For Your Next Test

1. The normal force is equal in magnitude and opposite in direction to the component of gravitational force perpendicular to the surface when there is no vertical acceleration.
2. On an inclined plane, the normal force is reduced by a factor of $\cos(\theta)$ where $\theta$ is the angle of inclination.
3. Normal force can be altered by additional vertical forces such as applied pushes or pulls.
4. In equilibrium scenarios, the sum of forces in any direction must be zero, making the normal force a crucial part of solving for unknowns.
5. Normal force does not always equal weight; it depends on additional vertical forces and the orientation of surfaces.

Review Questions

• How does the angle of an inclined plane affect the normal force acting on an object?
• What happens to the normal force when additional vertical forces are applied to an object?
• Why doesn't normal force always equal weight?

Related terms

Friction:

A resistive force that acts parallel to two surfaces in contact and opposes their relative motion.

Gravitational Force:

The attractive force acting between any two masses due to gravity, typically experienced as weight.

Newton's Third Law:

$\text{For every action, there is an equal and opposite reaction.}$ Normal force can be considered as a reactionary force to gravitational pull or other applied forces.