Q.What is friction? Define coefficient of static friction and coefficient of kinetic friction. Give the necessary formula for each.

Step 1. Friction is the property which resists (opposes) relative motion between two surfaces in contact — the resulting opposing force is called frictional force.

Step 2. When a body is at rest under an applied force $F$, the balancing force is static friction $F_s$; as $F$ increases, $F_s$ self-adjusts to match it, up to a maximum called the limiting force of friction $F_L$. The coefficient of static friction is defined as $\mu_s = \dfrac{F_L}{N}$, where $N$ is the normal reaction between the surfaces; equivalently $F_L = \mu_s N$.

Step 3. Once the body is sliding, the opposing force is kinetic friction $F_k$, generally somewhat smaller than $F_L$ for the same surfaces. The coefficient of kinetic friction is defined as $\mu_k = \dfrac{F_k}{N}$; equivalently $F_k = \mu_k N$. …

Define friction generally, then give the defining ratio and formula for each …

Defining μs and μk without reference to the normal reaction N — both coefficients are specifically the ratio of the fr …