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How to calculate Friction Force ?

Last Updated : 23 Jul, 2025

Friction is a force that acts to slow down the movement of two objects that are in contact. There are two types of friction: Static and Kinetic. When friction is powerful enough to inhibit movement between two objects, it is called static friction. When the frictional force is insufficient to halt all motion, kinetic friction is applied; heat generation is one of the effects of kinetic friction.

Friction Formula Physics

Ff = μη

Where,

Ff = force of friction acting on the object

μ = coefficient of friction

η = normal force acting on the object

Solved Examples

1. A child is pulling a box of mass 10 Kg. What is the standard force acting, and also calculate the frictional force if the coefficient of friction μ is 0.3?

Mass, m = 10 Kg,
Normal force is given by Fn = mg
= 10 Kg × 9.8 m/s2
= 98 N.
The Frictional force is articulated by Ff = μ Fn
= 0.3 × 98 N.
= 29.4 N.

2. Nancy of mass 40 Kg is slipping on the frost. If the coefficient of friction acting is 0.45. Find the frictional force acting between her and the frost layer?

Mass m = 40 Kg
Coefficient of friction μ = 0.45
The Normal force is articulated by Fn = mg
= 40 Kg × 9.8 m/s2
= 392 N.
The Frictional force is articulated by Ff = μ Fn
= 0.45 × 392 N
= 176.4 N.

3. A force of 100N is applied to a box on the floor with a friction coefficient of 0.2. Calculate the friction force.

The normal force Fn=100 N
Coefficient of friction= 0.2
Friction force (Ff) = μ Fn
= 0.2 x 100
=20 N

4. A force of 60N is applied to a box that is resting on the floor and has a coefficient of friction of 0.4. Calculate the friction force.

The normal force Fn=60 N
Coefficient of friction= 0.4
Friction force (Ff) = μ Fn
= 0.4 x 60
= 24 N

5. A boy pulls a body of mass 50Kg resting on a flat horizontal surface. Calculate the frictional force if the coefficient of friction is 0.3.

 Mass of the body m = 50Kg 
Coefficient of friction  =0.3.
The friction formula is given as  
Ff = μ × Fn
Here N is the normal force given by the formula  
N = m×g  
'g' is the acceleration due to gravity = 9.81 m/s2
So , N = 50 × 9.81 
= 490.5 Kg m/s2
= 490.5 N
Now substituting the values in the friction formula we get the required frictional force
F = 0.3 × 490.5 N
= 147.15N

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