# Frictional Torque at the axle

1. Aug 21, 2009

### Amar.alchemy

Let us consider a wheel which rotates about an axle thorugh its center with an angular velociy $$\omega$$0. After sometime it comes to rest due to the frictional torque at its axle.
Now, if we go by the defination of torque than it is defined as:
$$\tau$$= r x F. Since the frictional torque is exerted along the axle, we can take the value of r as 0. Then there will not be any frictional torque. Kindly explain me??

2. Aug 21, 2009

### Staff: Mentor

No you can't. Real axles with friction have non-zero radii.

3. Aug 21, 2009

### Amar.alchemy

ok so, Frictional Torque is equal to the cross product of radius of axle and frictional force... Thanks :-)