Friction

Definition

Friction is the resistive force that opposes the relative motion or tendency of such motion of two surfaces in contact. It acts parallel to the surfaces and opposite to the direction of motion.

5 Must Know Facts For Your Next Test

1. Friction can be categorized into static friction (before motion starts) and kinetic friction (during motion).
2. The coefficient of friction ($\mu$) is a dimensionless scalar value that represents the ratio between the force of friction and the normal force.
3. Static friction is generally greater than kinetic friction for the same materials.
4. The force of kinetic friction is calculated using $f_k = \mu_k N$, where $\mu_k$ is the coefficient of kinetic friction and $N$ is the normal force.
5. Frictional forces generate heat due to energy dissipation during contact between surfaces.

Review Questions

• What are the main differences between static and kinetic friction?
• How do you calculate the force of kinetic friction in a system?
• Why is static friction typically greater than kinetic friction for two given materials?

Related terms

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

Coefficient of Friction: A dimensionless scalar value representing the ratio between the force of friction and normal force for two specific surfaces.

Kinetic Energy: $\text{Energy possessed by an object due to its motion, given by } \frac{1}{2}mv^2, \text{where } m \text{is mass and } v \text{is velocity.}$