I've seen Consistent method for finding direction of static friction which was the closest question I could find, but I'd like something better. I need a method which :
1) Intuitively makes sense
2) Works for circular motion
3) Works for rolling without slipping
4) Works for most other simple cases
I'd like the method to work out the direction of friction in these cases :
1) A box is placed on a flat surface and pushed to the right.
2) A mass placed on a turntable rotates without slipping with respect to the turntable.
3) A mass is placed on a flat surface and a string is attached to it. It is then rotated so that it moves in a horizontal circle.
4) A wheel, driven by some force F, is moving to the right on a flat surface without slipping.
5) A wheel is rotating down an inclined plane without slipping.
6) A wheel is rotating up an inclined plane without slipping.
7) A car enters a banked curve with a speed greater than the required speed for circular motion with no friction (what I mean by 'no friction' is that even if there were no friction, the car would perform circular motion about the center as the speed is ideal).
8) A car enters a banked curve with a speed less than the required speed for circular motion with no friction.
I'm very weak when it comes to determining this direction if there is rolling without slipping, rolling with slipping, or circular motion. For one, I don't think I'm even clear on what slipping means.. I've always thought that I can think of static friction as something which opposes the relative motion between two bodies, but in these cases, it generally doesn't work.