Newton’s cradle is a device demonstrating the conservation of energy and momentum.
In an ideal Newton’s cradle, only the two balls on the end will move and there will be no energy loss, resulting in the cradle going on for an infinite amount of time. However, in a real Newton’s cradle, the fourth ball does have some movement and there is slight reverse movement as seen in the picture above. The equations p=mv and KE=½mv2 can be used to help find the velocities of the two end balls on an ideal Newton’s cradle, with perfectly elastic objects so there is no loss. The type and size of the balls does not affect the solution as long as the material is still elastic and doesn’t have too much mass.