Here is another problem I'm struggling with: A mass m is sitting on an rough incline of mass M who in turn is resting on a frictionless surface. What minimum force F must be applied to the non-inclined side of the incline to make mass m move up the incline. The coefficient of static friction between m and M is [itex]\mu[/itex] and the incline has a slope that makes an angle [itex]\theta[/itex] with the horizontal. Let [itex]a_i[X][/itex] be the net acceleration of object [itex]X[/itex] along the [itex]i[/itex]-axis. Since m is moving up the incline while M is moving, then I must have [tex] 0 < a_x[m] < a_x[M][/tex], and [tex]a_y[m] > 0[/tex].Unfortunately, I don't get the right answer when I solve for F starting from these initial arguments. I don't know what else to do. Any help?