Here is the situation: An airplane flies in a loop (a circular path in a vertical plane) of radius 150 . The pilot's head always points toward the center of the loop. The speed of the airplane is not constant; the airplane goes slowest at the top of the loop and fastest at the bottom. Here is the question: At the top of the loop, the pilot feels weightless. What is the speed of the airplane at this point? There is a similar question already asked on this forum but i had a few additional questions about this. I have a free body diagram with the plane at the top of the loop and the force that is acting on it is its weight (gravity). The similar post does not include the normal force that would oppose weight. Is the normal force excluded because the plane is in the air and therefore there is no normal force? Thank you for helping me understand this concept.