Question

A box has a weight of 120 N and is being pulled across a horizontal floor by a force that has a magnitude of 100 N. The pulling force can point horizontally, or it can point above the horizontal at an angle θ. When the pulling force points horizontally, the kinetic frictional force acting on the box is twice as large as when the pulling force points at the angle θ. Find θ.

Answer 1

A = 0o: Fn = Wb = 120 N. = Normal force

Fn = 120-F*sin A = 0.5*120.
120-100*sin A = 60.
-100*sin A = -60.
sin A = 0.60.
A = 36.9o.