A box of mass 32.0 kg sits on a horizontal steel ramp 3.4 m long with a coefficient of static friction of 0.30 between the ramp and the box. The end of the ramp is slowly lifted until the box begins to slide down the ramp. What angle does the ramp make with the ground when this happens? What i have so far: In the x-direction there is a frictional force of -.30 and a force of mgsin(&theta). How can i determine if the box will move with the angle. F - fr = ma?