1. The problem statement, all variables and given/known data A spool of wire rests on a horizontal surface as in Figure P10.87. As the wire is pulled, the spool does not slip at the contact point P. On separate trials, each one of the forces F1, F2, F3, and F4 is applied to the spool. For each one of these forces, determine the direction the spool will roll. Note that the line of action of F2 passes through P. http://www.webassign.net/pse/p11-68.gif 2. Relevant equations Concepts Only 3. The attempt at a solution I actually have the answers, I simply do not understand how to get to them. F1, F3, and F4 all pull perpendicular to the axis of rotation in a counter-clockwise direction. My logic says that that would create a counter-clockwise rotation and friction would push the ball to the left. This is true for F3 and F4, but not for F1 (which the key says moves right). I think I understand F2, but because I don't understand the others I want to make sure my reasoning is sound. I believe the perpendicular component of the force would act in the same way I described above rolling the ball left, but the force component going through the axis of the center of mass would roll the ball to the right. Because the force is at a 45 degree angle (because it starts at point P), the components are equal and the ball won't move.