Static friction

Definition

Static friction is the force that resists the initiation of sliding motion between two surfaces in contact. It acts when an object is at rest relative to a surface and prevents it from moving.

5 Must Know Facts For Your Next Test

1. Static friction has a maximum value given by $f_s \leq \mu_s N$, where $\mu_s$ is the coefficient of static friction and $N$ is the normal force.
2. The coefficient of static friction ($\mu_s$) is typically greater than the coefficient of kinetic friction ($\mu_k$).
3. Static friction adjusts to match the applied force up to its maximum limit, preventing motion until this limit is exceeded.
4. It plays a crucial role in scenarios involving inclined planes, where it can prevent objects from sliding down.
5. Static friction does not do work because there is no displacement while it acts.

Review Questions

• What determines the maximum value of static friction?
• How does static friction differ from kinetic friction in terms of their coefficients?
• Why does static friction not perform any work?

Related terms

Kinetic Friction: The force that opposes the movement of two surfaces sliding past each other. It acts on moving objects.

Normal Force: The perpendicular contact force exerted by a surface on an object resting on it.

Coefficient of Friction: \(\mu\), a dimensionless scalar value representing the ratio of the force of friction between two bodies and the normal force pressing them together.