An airplane is flying in horizontal flight at a constant velocity. The weight of the airplane is 40,000 N. The wings produce a lift force that is perpendicular to the wings and a drag force that is parallel to the wings. The engine produces a forward thrust force of 2,000 N. Which of the following statements is true?
A) The lift force on the airplane is zero.
B) The drag force on the airplane is zero.
C) The lift force on the airplane is 42,000 N upward.
D) The drag force on the airplane is 38,000 N downward.
E) The drag force on the airplane is 2,000 N backward.

Question

Quizplus · Accepted Answer

For an airplane in horizontal flight at a constant velocity, the lift force must balance the weight of the airplane, and the thrust force must balance the drag force. Since the weight is given as 40,000 N, the lift must also be 40,000 N to keep the airplane in level flight, not 42,000 N, eliminating option C. The drag force is not given as a specific value related to the weight directly, but since the airplane is in steady flight with a forward thrust of 2,000 N, this thrust must be balancing out the drag force, making it also 2,000 N backward, which matches option E. Options A and B are incorrect because the lift and drag forces cannot be zero for an airplane in flight, and option D is incorrect because it misrepresents the direction and magnitude of the drag force.

An Airplane Is Flying in Horizontal Flight at a Constant