Practice Friction in Physics
Use these practice problems to test your method after reviewing the concept explanation and worked examples.
Quick Recap
A contact force that opposes the relative motion or tendency of motion between two surfaces in contact.
The resistance you feel when sliding something across a rough surface — it always acts opposite to motion.
Example 1
mediumA 20 \text{ kg} box sits on a surface with a coefficient of kinetic friction \mu_k = 0.3. What force is needed to pull it at constant velocity?
Example 2
hardA 15 \text{ kg} block on a surface (\mu_k = 0.25) is pushed with 80 \text{ N}. What is the acceleration?
Example 3
mediumThe coefficient of static friction between a box and the floor is \mu_s = 0.4. If the box weighs 98 \text{ N}, what is the maximum static friction force?
Example 4
mediumA 12 \text{ kg} crate is pulled across a level floor at constant speed by a horizontal 29.4 \text{ N} force. What is the coefficient of kinetic friction?