Do spinning tops with sharp tips experience less torque than wider tips? Let's say a spinning top is perfectly stationary, with no air resistance or other factors. As a result of friction between its tip and the surface, the top would then slow down. Would a sharp tip result in less torque then a wider tip then?
Since I couldn't find a distinct category for "rotational friction" or the such, I thought of the rotation as a linear contact between tip and surface when the circumference is "rolled out". This would use the friction formula F =  μ*Fn. This is constant for a tip of any surface area, and I think it would apply if the top were moving linearly instead of staying still (still a bit confused on it though).
However, since this is just counteracting the spin of the top, torque = F*r. So by my thought process, the sharp tip would have a smaller r (force applied perpendicularly on circumference) which would mean it would experience less torque. But this would also mean that a tip with near-zero thickness experiences much less torque, which doesn't seem to be true empirically. Any help is appreciated!
 A: Friction is a complex topic.
Consider atomically clean metal surfaces in high vacuum. They would weld on contact.
Consider that same surfaces in air. About a nanosecond later, they would be covered by a layer of oxide which would radically change the behavior. So the composition of the top layers and and dirt and/or lubricants on the top layers matters.
Two flat surface are not atomically flat. They have a degree of roughness, even with a mirror polish. They only touch where two high spots meet. The high spots need not stick up far enough to see. Pressure on those high spots can be enough to melt the metal at that spot, making a microscopic weld. This is a source of static friction.
Empirically, dynamic friction is proportional to the pressure. If you reduce the tip area, you increase the pressure. You might expect torque to be constant. But you find empiracally that smaller tips have less friction. On the other hand, car tires with larger contact patches have more traction.
Sorry, I don't have an easy answer.
