A sailboat can be propelled into the wind by a maneuver called beating to windward. Beating requires the sailboat to travel in a zigzag pattern at an angle to the wind that is greater than the no-go zone, which is shaded red in FIGURE 7-23. When a sailboat is just outside the no-go zone (boats B in the figure) the wind exerts a force F(vector) on the sail that has a component in the direction of motion V(vector). Similar comments apply to boats C. The work done by the wind on the sail is W = Fd cosθ, and because v = d/t, the propulsion power P = W/t delivered to the sailboat is Fv cos θ, where θ is the angle between the sail force and the direction of motion.

(a) Assuming that F and v have the same magnitudes for each sailboat, will the propulsion power delivered to sailboats B be greater than, less than, or the same as the propulsion power delivered to sailboats C? Explain.

(b) If F = 870 N and v = 11 m/s, what propulsion power is delivered to sailboats B, for which θ = 79°?

(c) What propulsion power is delivered to sailboats C, for which θ = 56°?