Uploaded January 2010 | Updated September 2026, 2 weeks ago
Comparing the bounce of smooth balls and rubber super-balls. First a smooth metal ball is thrown without rotation toward a parallel set of surfaces (floor and ceiling). The smooth metal ball acquires a slight clockwise rotation, but continues with its forward motion and bounces from floor and ceiling, moving to the right. A ping pong ball entering at an angle from the left bounces from both surfaces, but stops its forward motion and ends up bouncing vertically up and down. However, when a superball enters from the left at an angle (but without any spin) it acquires clockwise spin after the first bounce, but when it reaches the second (top) surface it reverses both its linear direction (now moving left) and its spin (changes to counterclockwise). After the third bounce from the floor it continues left but loses almost all of its spin and ends up returning almost to its original starting point with nearly the same velocity as it started with. Simple application of the conservation of linear and angular momentum. Physics is so cool!
Comparing the bounce of smooth balls and rubber super-balls. First a smooth metal ball is thrown without rotation toward a parallel set of surfaces (floor and ceiling). The smooth metal ball acquires a slight clockwise rotation, but continues with its forward motion and bounces from floor and ceiling, moving to the right. A ping pong ball entering at an angle from the left bounces from both surfaces, but stops its forward motion and ends up bouncing vertically up and down. However, when a superball enters from the left at an angle (but without any spin) it acquires clockwise spin after the first bounce, but when it reaches the second (top) surface it reverses both its linear direction (now moving left) and its spin (changes to counterclockwise). After the third bounce from the floor it continues left but loses almost all of its spin and ends up returning almost to its original starting point with nearly the same velocity as it started with. Simple application of the conservation of linear and angular momentum. Physics is so cool!
