The loop of death
Place the ball at any point of the inclined plane and let it fall. Observe the motion of the ball. Try to find a starting point that will make the ball:
- Rise to a certain height and then roll down, staying in the loop.
- Fall from the top part of the loop.
- Ride the whole loop.
How it works
There are two forces acting on the ball in the loop: gravity (directed vertically downwards) and centrifugal force (directed outwards from the loop). For the ball to ride the whole loop, the magnitude of the centrifugal force acting on the ball in the top section must exceed the gravity. The magnitude of centrifugal the force depends on the mass of the ball, the radius of the loop (these values are constant) and the squared ball speed. Hence, the rolling ball needs sufficient speed to ride the whole loop.
This effect is applied in roller coasters in amusement parks.