# Car Rolling Friction

1. Nov 14, 2008

### impel123

Hello guys,

I would like to help me with rolling friction on a car(i am building a project that simulates the forces
applied to a vehicle when it moves on a straight road http://rapidshare.de/files/40862186/Vehicle_Sim.zip.html).

So:

Engine has a torque at some RPM,and the torque goes to the wheels with gearbox.If car weights 1000kg,and
rolling friction coefficient is 0.03, then total friction force for all 4 wheels is 1000*9.81*0.03=294N.

1)what happends if torque on wheels from engine in certain RPM is 190N (<=294)?friction then is 0 or 190 or 294?
2)friction depends on speed?
3)when a apply brake,and brakes make car slows down with acceleration=9m/s^2,friction force changes direction?
4) if friction is 294N and car speed=0,and driver presses acceleration pedal but the torque on wheels is only 100N,
the car will never roll?

thanks a lot!

Last edited by a moderator: Apr 23, 2017
2. Nov 15, 2008

### Sir_Arthur

1) If friction is preventing the car from moving, then the frictional torque is equal to the torque it is acting against (190)
2) Static (unmoving) friction depends on the force it is opposing, because friction never adds energy to a system and can only oppose the other forces acting on it. Once the car is moving, the frictional force does not very with speed
3) Yes, when braking, the frictional force reverses direction
4) Unless the force of friction can be overcome, the car will not move

3. Nov 15, 2008

### impel123

Thank You so much

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