Why a Glass Ball Bounces Higher Than a Rubber Ball

This glass ball bounces higher than a rubber ball of the same size. (John Morgan)
This glass ball bounces higher than a rubber ball of the same size. (John Morgan)

A glass ball bounces higher than a rubber ball of the same size, providing it does not break. Surprised? You can certainly test it out for yourself, using a marble and a small rubber ball! Further, a steel ball will also bounce higher than a rubber ball. Yet, we don’t go around using ball bearings and marbles as balls because they can easily damage whatever they strike. To understand how it works, let’s start with bouncing…

Why Objects Bounce

Bouncing is a form of elastic collision between two objects. When you drop a ball, it will only bounce if it gets back the energy it imparted to the surface it hit. Many objects dissipate energy too readily to bounce well. You can gauge how well a material retains energy by striking it with a mallet or a spoon. Do you hear a ringing sound? That vibration is energy. The longer it lasts, the better the material is likely to be at bouncing.

If you had a bell made of rubber, one of glass, and one of steel, you’d hear a nice ringing sound after striking the glass and metal bell. The rubber bell… not so much.

Why Glass and Steel Bounce Better Than Rubber

When a rubber ball hits a surface, it compresses and deforms before returning to its original shape. Quite a lot of energy is lost in this process. Although it is not a crystal like its chemical relative, quartz (SiO2), glass is rigid and does not deform much when it strikes a surface. Most of the energy of the impact returns to the glass. Steel is crystalline, especially hardened steel containing carbon, so it deforms slightly but retains a lot of the collision energy. Of course, the bouncy advantage is lost if a glass or steel ball is hurled with force because glass will break and dense steel will have enough momentum to become a weapon.

Test It for Yourself

How well a ball bounces also depends on the surface it strikes. Energy can be lost to the flooring material. A surface that has a bit of “give” to it, like linoleum, will absorb more energy than a hard surface, like tile, but will be less liable to break a glass ball.

You can test the bounce of balls on a hard surface providing you drop a rubber ball, a solid glass ball, and a steel ball from the same (low) height. Think millimeters or centimeters, not meters. Use care, since a glass ball may break or chip, even when dropped a small distance. Eye protection is encouraged. Measure the height of the bounces.

You may also wish to include a bouncy ball in your test. These balls are made of a polymer that bounces better than natural rubber.