Q:

Select the correct answer.An airplane is traveling at a speed of 240 miles/hour with a bearing of 110°. The wind velocity is 56 miles/hour at a bearing of 325°. What are the plane's actual speed and direction angle?A. The speed is 179.82 miles/hour, and the direction angle is 100.60°.B. The speed is 179.82 miles/hour, and the direction angle is 349.40°.C. The speed is 196.77 miles/hour, and the direction angle is 115.60°.D. The speed is 196.77 miles/hour, and the direction angle is 349.40°.

Accepted Solution

A:
Velocity of the plane relative to the air:[tex]\vec v_{P/A}=240(\cos110^\circ,\sin110^\circ)\,\mathrm{mph}[/tex]Velocity of the air relative to the Earth:[tex]\vec v_{A/E}=56(\cos325^\circ,\sin325^\circ)\,\mathrm{mph}[/tex]Velocity of the plane relative to the Earth:[tex]\vec v_{P/E}=\vec v_{P/A}+\vec v_{A/E}[/tex][tex]\vec v_{P/E}=(240\cos110^\circ+56\cos325^\circ,240\sin110^\circ+56\sin325^\circ)\,\mathrm{mph}[/tex][tex]\vec v_{P/E}\approx(-36.21,193.41)\,\mathrm{mph}[/tex]The plane's speed is[tex]\|\vec v_{P/E}\|\approx\sqrt{(-36.21)^2+193.41^2}\approx196.77\,\mathrm{mph}[/tex]and its direction [tex]\theta[/tex] is given by[tex]\tan\theta\approx\dfrac{193.41}{-36.21}\implies\theta\approx100.6^\circ[/tex]I think there may be a typo in one of the answer choices. The closest answer would probably be C. Someone must have dropped the ball when coming up with the question...