Question

Why are the loops on a roller coaster tear-drop shaped instead of circular? It would be simpler to design & build tracks with a circular shape, so why do roller coaster manufacturers use a tear-drop shape instead? Be specific, and include a discussion of the forces acting on the rider, their centripetal acceleration, etc. as needed to make your point.

Answer 1

The centripetal force acting on the rider is much greater if the roller coaster has a circular loop, rather than oval. This is because the change in direction is much sharper throughout the loop, causing the rider to experience a much more intense G-Force throughout the loop. 
A teardrop loop features a more gradual change of direction: the cart spends time moving upward, briefly changes direction, and spends the rest of the time moving downward and flattening to a horizontal path. This means the riders experience the majority of the force on the way down as the car levels out, rather than an intense G-force throughout the ride.