(The degrees is 35.8) So far I thought that i'd solve it like this: Weight of block W = mg Component of W parallel to slope = Wsinθ Component of W perpendicular to slope = Wcosθ Call R the normal reaction force of the slope on the block. In the direction perpendicular to the slope, the force are balanced: R = F + Wcosθ The limiting frictional force, Fr is: Fr = μR = μ(F + Wcosθ) In the direction parallel to the slope, when on the point of slipping the limiting frictional force is just balanced by the component of W parallel to slope: Fr = Wsinθ μ(F + Wcosθ) = Wsinθ μF + μWcosθ) = Wsinθ μF = Wsinθ - μWcosθ) . . = W(sinθ - μcosθ) F = W(sinθ - μcosθ)/μ . = mg(sinθ – μcosθ)/μ However, when I plug in all of my numbers, I get -215N. And when I put that into my homework, it is wrong. Is this a computational error, was my formulas flawed?