# Frictional Force of a Rolling Object

I'm not sure that I understand this problem:

A spool of wire of mass 4.7kg and radius 0.99m is unwound under a constant wire tension 10N. Assume the spool is a uniform solid cylinder that rolls without slipping. Find the friction force on the bottom of the spool.

(Note that the wire is coming out of the top of the spool)

The frictional force is equal to the coefficient of friction * the normal force.

I can easily find the normal force by multiplying the mass times 9.8 m/s^2, but nowhere does the problem state the coefficient of friction.

Aside from that, a rolling object isn't affected by the frictional force. I tried 0 and that's not the answer, so there is a frictional force here.

What am I missing here? There doesn't seem to be nearly enough information to calculate the frictional force.

If you look at your picture and if $F$ was the only force which was acting then the linear acceleration $a$ of the centre of mass would be given by $F = Ma$ and the angular acceleration about the centre of mass would be given by $FR = I_{cm} \alpha = \frac 12 MR^2 \alpha$.
The no slipping condition $a = R \alpha$ is not satisfied so there must be another force present - the static frictional force between the object and the ground.