Static Friction Formula

The force that opposes movement in between surfaces when these surfaces are at rest is called static friction. It opposes each applied force with the opposite direction of motion desired and varies from zero to a maximum value depending on the normal force acting between materials in contact. This force is essential in the performance of day-to-day activities being able to walk without slipping, in vehicles holding their traction on roads.

Formula 

Static friction is the resisting force encountered in a body which is at rest. It is represented as

Where,

• static friction is Fs

• the coefficient of static friction is μs

• the normal force is Fn

Static Friction Formula enables one to calculate the frictional force, coefficient of friction, or normal force in any requested numerical.

Static Friction Solved Examples

Problem 1: A box of snacks weighing 5 kg with a force of 200 N is still on the floor. Using a coefficient of friction of 0.3, calculate the static friction.

Solution:

Given, 

Fn (Normal force) = 200 N,

μs  (Coefficient of friction) = 0.3,

Fs =μs  Fn

= 0.3 × 200 N

Fs = 60 N.

Problem 2: A boy is dragging a toy car that weighs 4 kg. The car was originally at rest on the ground. When the static frictional force was 50 N, determine the value of the friction coefficient.

Solution: 

Given

m (Mass) = 4 kg,

Fs  (static frictional force) = 50 N,

Fn (Normal force) = mg

= 4 Kg × 9.8 m/s2

Fn= 39 N

μs = Fs /Fn

μs = 50/39

μs  = 1.282