Spinning Object on Flat Surface

[domoarigato]

I'm working on a computer simulation, but I'm not sure how to approach this problem. I want to find the change in angular velocity on an object rotating on top of a flat plane.

So far this is what I have:
(* == multiplication not dot product)

Ff x r = I * alpha
Ff x r = I * dv/dt

I can find I, Ff, and dt. I assume Ff x r can be reduced to Ff * r because the friction will always be perpendicular. I don't know what r is though, because the object is flat aren't there a ton of different particles experiencing the Ff? I'm I going to have to integrate all the little Ff x r? I'm pretty lost. Any direction would be wonderful.

 

[Chi Meson]

I'm working on a computer simulation, but I'm not sure how to approach this problem. I want to find the change in angular velocity on an object rotating on top of a flat plane.

So far this is what I have:
(* == multiplication not dot product)

Ff x r = I * alpha
Ff x r = I * dv/dt

I can find I, Ff, and dt. I assume Ff x r can be reduced to Ff * r because the friction will always be perpendicular. I don't know what r is though, because the object is flat aren't there a ton of different particles experiencing the Ff? I'm I going to have to integrate all the little Ff x r? I'm pretty lost. Any direction would be wonderful.

Instead of Ff x r, just use frictional torque, which is what Ff x r is. How would you measure Ff anyway?

 

[domoarigato]

Thank you very much for your reply.
I think Ff is what is confusing me. I know the friction coeffecient, and I know how to find the normal. How can I find the friction torque? If ForceOfFriction = NormalForce * FrictionCoeffecient, what does the FrictionTorque = ?