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Formula of Friction Force

The formula for friction force is,

Where,

• F_f is the friction
• μ is the coefficient of friction force
• F_n is the normal force

It is a vector quantity.

Friction Force – Solved Examples

Let us answer some problems with a friction force.

Problem 1: An object of mass 10 kg is moving through a surface. Compute the friction force if the coefficient of friction is 0.2?

Answer:

Known variables are,
m = 10 kg and μ = 0.2
The friction force formula is,
F_f = μF_n
Fn can be computed as,
Fn = mg
= 10×9.81 = 98.1 N
So, F_f = 0.2×98.1 = 19.62 N

Friction force F_f is 19.62 N

Problem  2: Calculate the friction force of a 5 kg body which is moving through a surface with a friction coefficient 0.3?

Answer:

Known variables are,
m = 5 kg and μ = 0.3
The friction force formula is,
F_f = μF_n
F_n can be computed as,
F_n = mg
= 5×9.81 = 49.05 N
So, Ff = 0.3×49.05 = 14.715 N

Friction force F_f is 14.715 N