Friction: a Person Is Dragging a Packing Crate of Mass

Multiple Choice

Friction: 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°