Kinetic friction

Definition

Kinetic friction is the force that opposes the relative motion between two surfaces in contact when they are moving past each other. It acts parallel to the surfaces and opposite to the direction of motion.

5 Must Know Facts For Your Next Test

1. The coefficient of kinetic friction ($\mu_k$) is usually less than the coefficient of static friction ($\mu_s$).
2. The force of kinetic friction can be calculated using $f_k = \mu_k N$, where $N$ is the normal force.
3. Kinetic friction depends on both the nature of the surfaces in contact and their relative speed.
4. Unlike static friction, kinetic friction remains constant regardless of the applied force once motion starts.
5. In problems involving inclined planes, kinetic friction plays a crucial role in determining acceleration.

Review Questions

• How does kinetic friction differ from static friction?
• What formula is used to calculate the force of kinetic friction?
• Why is it important to consider kinetic friction when analyzing motion on an inclined plane?

Related terms

Static Friction:

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

Normal Force:

The perpendicular force exerted by a surface on an object in contact with 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.