Since the box will move only in the horizontal direction and no net vertical motion then the force for the horizontal motion is equal to fcos θ. then this force is equal to the normal force and friction force exerted by the floor.fcos θ = us (Mg + fsin θ)fcos θ = us Mg + us fsin θfcos θ - us fsin θ = us Mgf(cos θ - us sin θ) = us mgf = us Mg/ (cos θ - us sin θ)
1. Use distributive property to multiply the parentheses. You’ll end up with 5z+12.5=5z+12.5. 2. You’ll notice the equation equals each other. 5z-5z equals zero, same for 12.5.
