Kinetic friction

Definition

Kinetic friction is the force that opposes the relative motion of two surfaces sliding past each other. It acts parallel to the surfaces in contact and depends on the nature of the materials and normal force.

5 Must Know Facts For Your Next Test

1. The coefficient of kinetic friction ($\mu_k$) is typically less than the coefficient of static friction ($\mu_s$).
2. The magnitude of kinetic friction is given by $f_k = \mu_k N$, where $N$ is the normal force.
3. Kinetic friction always acts in a direction opposite to the direction of motion.
4. Unlike static friction, kinetic friction has a constant value for a given pair of surfaces and normal force.
5. Kinetic friction converts kinetic energy into thermal energy, leading to wear and heat generation between sliding surfaces.

Review Questions

• What is the relationship between kinetic friction and normal force?
• How does kinetic friction differ from static friction?
• Why does kinetic friction generate heat during sliding?

Related terms

Static Friction:

The force that resists the initiation of sliding motion between two surfaces in contact.

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 force pressing them together.