Coefficient Of Static Friction Formula

Static Friction is friction which is experienced when an object is placed on a surface. And, Kinetic friction is due to the movement of an object on a surface. Friction is well characterized by the coefficient of friction and is explained as the ratio between the frictional force and the normal force. This helps the object to lie on a surface. The coefficient of static friction is a scalar quantity and denoted as μs.

Formula of Coefficient of Static Friction

The formula for the coefficient of static friction is expressed as

μ_s = F /N

Where

μ_s = coefficient of static friction

F = static frictional force

N = normal force

Solved Examples on Static Frictions

Question 1: An object having a mass of 10 kg is placed on a smooth surface. Static friction between these two surfaces is given as the 15 N. Find the coefficient of static friction?

Solution:

Given

m = 10 kg

F = 30 N

μ_s = ?

We know that,

Normal force, N = mg

So, N = 10× 9.81 = 98.1 N

The formula for coefficient of static friction is,

μ_s = F/N

μ_s= 30/98.1

μ_s = 0.305

Question 2: The normal force and the static frictional force of an object are 50 N and 80 N respectively. Find the coefficient of static friction?

Solution:

Given

N = 50 N

F = 80 N and μ_s = ?

The formula for coefficient of static friction is

μ_s = F /N

μ_s = 80/50

μ_s = 1.6