A pilot flies a small plane in a vertical loop of radius r. At the top of its trajectory he experiences weightlessness. If the acceleration due to gravity is g, the speed of the plane at the top of its trajectory would be

A pilot flies a small plane in a vertical loop of radius r. At the top

1.	A pilot flies a small plane in a vertical loop of radius r. At the top of its trajectory he experiences weightlessness. If the acceleration due to gravity is g, the speed of the plane at the top of its trajectory would be
A.	zero
B.	infinite
C.	√gr
D.	√2gr
Answer» D. √2gr