Physics / Static & Kinetic Friction

What’s the difference between static and kinetic friction?

Static friction is friction that resists movement, while kinetic friction is friction during movement.

Is the coefficient for static friction (μ_s) or kinetic friction (μ_k) larger, and why?

The coefficient for static friction (μ_s) is larger than that for kinetic friction (μ_k) because static friction must overcome the initial resistance to start motion, while kinetic friction acts on objects already in motion.

What’s the equation for static frictional force (F_fs)?

F_fs = μ_s * F_N

What is the coefficient of static friction and coefficient of kinetic friction?

The coefficient of static friction (μs) is the amount of force needed to move an object from rest. The coefficient of kinetic friction (μk) measures the force opposing motion of an object already in motion.

Equation for net force (F_net or ΣF) using applied force & kinetic friction (F_fk).

ΣF: F_app - F_fk

Three cars (car L, car M, and car N) are moving with the same speed and slam on their brakes. The most massive car is car L, and the least massive is car N. If the tires of all three cars have identical coefficients of kinetic friction with the road surface, for which car is the amount of work done by friction in stopping it the greatest?

Car L, because Car L has the greatest kinetic energy.