Physics of a Bouncing Ball
Ping pong balls are tiny balls with an amazing bounce capability. These little white orbs are hollow on the inside, small in size, and made of a little-used plastic material called celluloid. Because of their unique properties, these balls bounce better than many rubber balls, yet are a fraction of the size and weight, making them ideal for indoor games.
Since the surface of a ping pong ball is stiff and springy, it loses less energy than a softer ball would when bouncing on a hard surface. The more energy the ball conserves, the higher the subsequent bounce will be. When you bounce a ping pong ball on hard surfaces such as a ping pong table or a tile floor, you will notice how high it flies, especially as more force is applied. But if you attempt to bounce this ball on a softer surface, such as a mattress or a carpeted floor, the cloth will absorb the energy that the ball conserved, causing it to bounce less or not at all.
From a physics perspective, the bounce capability of a ball will depend both on the size and material of the actual ball as well as the surface it is dropped on. Thanks to their small surface area, ping pong balls also experience less air resistance when they are airborne. Finally, ping pong balls are hollow on the inside, making them extremely lightweight, which again aids in conserving energy as they bounce.
Material of a Ping Pong Ball
Ping pong balls are made of celluloid, a lightweight, flexible plastic. An American inventor, John Wesley Hyatt, discovered this material in the late 1860s after he experimented with a mixture of cellulose nitrate and camphor. Although it is a tough, inexpensive product, celluloid is also extremely flammable because of unstable properties. Originally Hyatt wanted to use celluloid to replace the pricey ivory in billiard balls, but he discovered this fiery danger when billiard balls made with celluloid exploded upon colliding. Celluloid was later used for a variety of products, including combs, collars, photography film, and toys, but it was slowly replaced by newer synthetic polymers. Today, celluloid is mainly used in the manufacture of ping pong balls, and because it is much lighter than other materials and has great tensile strength (causing the surface to remain stiff upon impact), it allows the balls to soar upon impact.
Ping pong balls appear to be bouncier than most balls because of relative size, the material that they are made of, the surfaces that they are usually dropped upon, and because they are hollow on the inside. Although heavier rubber balls usually bounce better than lightweight balls, celluloid makes ping pong balls perform quite well, because it is stiff and springy at the same time. However, these balls do not bounce well on all surfaces. For example, if you bounce both a bowling ball and a ping pong ball on a trampoline, the bowling ball will bounce substantially higher. This is due to Newton's second law, which states that the acceleration of an object is directly proportional to the net force acting upon the object and inversely proportional to the mass of the object. A bowling ball will accelerate faster it because it has a larger mass than the ping pong ball, which makes a difference when dropped upon a springy, softer surface, since more energy can be returned to the ball.
Although celluloid is extremely flexible, it is also susceptible to cracking or shattering if too much force is applied. If you hit a ping pong ball with a heavy object, or if you hit it too hard, the ball is likely to crack or dent, preventing it from bouncing as well. Ping pong balls are also flammable, and should not be placed anywhere near an open flame. Direct heat will make them sizzle, crack or even explode.