A 1000-kg airplane moves in straight flight at constant speed.The force of air friction is 1800 N.The net force on the plane is:
A)0 N
B)11600 N
C)1800 N
D)9800 N
E)none of these

Question

Quizplus · Accepted Answer

Since the airplane is moving at a constant speed in straight flight, the net force acting on it must be 0 N. This is because, according to Newton's first law of motion, an object will remain at rest or in uniform motion in a straight line unless acted upon by a net external force. In this case, the force of air friction is balanced by the thrust of the airplane's engines, resulting in no net force.

A 1000-Kg Airplane Moves in Straight Flight at Constant Speed