A Person Is Dragging a Packing Crate of Mass 100

Multiple Choice

A person is dragging a packing crate of mass 100 kg across a rough horizontal floor where the coefficient of kinetic friction is 0.400.He exerts a force F sufficient to accelerate the crate forward.At what angle above horizontal should his pulling force be directed in order to achieve the maximum acceleration?

A) 21.8°
B) 27.7°
C) 30°
D) 34.5°
E) 45°