Question

An airplane is flying at a constant velocity through the air. What is the relationship between the magnitudes of the four forces shown in the diagram?
A. L = W; F < D
B. L = W; F = D
C. L = W = F = D
D. L = W; F > D

Answer 1

Answer:

(B) L=W; F=D

Explanation:

Since the airplane's velocity is constant, the airplane is not accelerating in any direction. In absence of acceleration, all forces acting on the plane are balanced so that the net forces in the horizontal and the vertical directions are zero. Given the drawing, this implies that

Forward force = Drag force (F=D)

Weight = Lift (W=L)

which corresponds to option (B)

(it is not C because nothing in the text says that the vertical and horizontal components have to have same magnitude)