Physics: calculating force of friction

The tutor shows a basic example of calculating friction.

The force of friction, Ff, on a flat surface is given by

Ff = μFN


μ = coefficient of friction (often looked up from a table, or given)

FN = normal force: pushing force from surface to object at 90° to surface

Nearly always, FN = mg, where

m = mass of object

g = acceleration due to gravity (typically 9.8m/s2 on Earth)

Example 1: Calculate the force of friction between the tires and the road, dry conditions (μ = 0.40), for a 1400 kg car.


Ff = μFN = μmg = 0.40(1400)(9.8)= 5488N or 5500N in sig figs

I’ll be covering more about friction in coming posts:)


Heath, Robert W. et al. Fundamentals of Physics. D.C. Heath Canada Ltd., 1981.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

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