# Homework Help: How to calculate friction of wheels of car?

1. Nov 10, 2009

### vissarion.eu

If car of mass m=1000 kg I want to accelerate to speed v=50 m/s then to me need to calculate friction of car axis on which puted wheels and friction of wheels into ground and air friction. So I suggesting such formula
m*a*t+k*m*a*S+c*m*a*S=m*a*t+k*0.5*m*v^2+0.5*c*m*v^2, where a is acceleration of car say a=10 m/s/s and S is distance which car made until got speed v=50 m/s and k is friction koeficient of car wheels inside car and to the ground and c is koeficient for air friction. I would give k=0.01 and c=0.0001 and t is 5 seconds. So total energy of car:
m*a*t+k*0.5*m*v^2+0.5*c*m*v^2= 1000*10*5+0.01*0.5*1000*50*50+0.0001*0.5*1000*50*50= 50000+12500+125= 62625 J.
If you can calculate better just calculate and show and don't blame my formula.

2. Nov 10, 2009

### Andrew Mason

To calculate the friction loss due to wheels you can give the car a known quantity of energy and then see how far it will coast on the flat. $mv^2/2d = F = \mu_kN$ (You have to be careful not to give it too much speed to begin as the air resistance could be significant).

The problem with factoring in the air resistance is that it is proportional to speed or speed^2. Kinetic friction force on the wheels is a constant force.

AM

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