1. The problem statement, all variables and given/known data You push down on a box at an angle 15° below the horizontal with a force of 650 N. If the box is on a horizontal surface and the coefficient of static friction is 0.7, what is the heaviest box you will be able to move? 2. Relevant equations F=ma 3. The attempt at a solution So I've solved this problem using Fnet which was 650cos15 for the horizontal force and then subtracted [tex](\mu_s)(9.80)(m)[/tex] The ma part goes to zero since it's not accelerating. Therefore I get [tex]650cos15 = (\mu)(9.80)(m)[/tex] and then solve for m. I thought that was it. But now that I thinking about it more, there is a vertical component for the force. I'd imagine that extra force would make the box seem to weigh more, thereby increasing friction, making the box weigh less. Do I factor that vertical force in? If so, how?