A uniform bar of mass m is supported by a pivot at its top, about which the bar can swing like a pendulum. If a force F is applied perpendicularly to the lower end of the bar as in the diagram, how big must F be in order to hold the bar in equilibrium at an angle θ from the vertical?

(a) 2mg 

(b) 2mg sin θ 

(c) (mg/2) sin θ 

(d) 2mg cos θ 

(e) mg/2) cos θ 

(f) mg sin θ