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Fully elastic collision of newtons cradle balance balls
newtons cradle balance balls is a tabletop demonstration device invented in the 1960s, in which five balls of equal mass are held in place by suspenders, in close proximity to each other.
Ideally, the physical process of a perfectly elastic collision satisfies the conservation of momentum and energy. If the masses of the two colliding balls are equal, the equations of conservation of momentum and conservation of energy can be solved simultaneously: the two balls exchange velocities after collision. If the collided ball was originally stationary, after the collision, the ball has the same speed as the colliding ball, and the colliding ball stops. A similar analysis can be done when multiple balls collide.
In fact, because the collision between the balls is not an ideal elastic collision, and there will be energy loss, the balls still have to stop in the end. This is also the core physics of newtons cradle balance balls!