I promise this isn't homework, it's actually for my research :-P Here goes:
When two bodies are in contact and *translate* with respect to each other, there is no dependence of friction on contact area, and Ff = mu*Fn.
Now, assume we have a block of wood on a table with mass m and we apply a torque to the block's center of mass, rather than a force. Assuming mass is constant and the coefficients of torsional friction are constant, does the friction torque depend on contact area? if so, why, and if not, why not?
When two bodies are in contact and *translate* with respect to each other, there is no dependence of friction on contact area, and Ff = mu*Fn.
Now, assume we have a block of wood on a table with mass m and we apply a torque to the block's center of mass, rather than a force. Assuming mass is constant and the coefficients of torsional friction are constant, does the friction torque depend on contact area? if so, why, and if not, why not?