Vice Versa Balls

 

These balls look and feel like two identical rubber balls, but don’t be deceived by what you see—one ball bounces and the other doesn’t. This kit also includes everything you need to make your own bouncing balls.

 

Experiments:

1. Drop each ball simultaneously from 12 inches off the ground. Which one bounces? Now drop the ball that bounces from 12 inches off the ground again. Observe how high the ball bounces each time. Does the height increase, decrease, or remain constant?

 

2. Compare the height the bouncing ball reaches after dropping it from 12 inches, 24 inches, and 36 inches off the ground.

 

3. Carefully throw the bouncing ball at the ground (not too hard, it could hurt someone or knock something over). Does it bounce higher than the height you released it at?
   
   
4. Mark which ball is the bouncing ball and which one is not. Put both balls in a freezer for 10 minutes. Drop each from 12 inches off the ground. What happens? Does the bouncing ball still bounce?

 

5. Race the balls down a slight incline. Which one wins the race?

 

6.     Try dropping the two balls on a soft chair or firm foam surface. Which ball now bounces the highest?

 

How to make your own bouncing ball:

This kit comes complete with a bouncing ball mold, two colors of crystal powder to make two bouncing balls, and detailed instructions. Just add water to instantly make your own bouncing balls. See how high they bounce.

 

How the Vice Versa Balls work:

A ball held in the air has the potential to move when released. This is called potential energy. When the ball is dropped, gravity pulls it towards the center of the earth. The energy of the moving ball is called kinetic energy. When the rubber ball’s descent is stopped by the floor, it is slightly flattened as its particles squeeze together. (Imagine dropping a ball of soft clay on the ground. Would it remain a ball or would it spread out on the ground?) Some of the kinetic energy the ball had on the descent becomes elastic potential energy. What happens next is determined by the properties of the ball.

 

Though they look the same, each ball is made of a different material. The ball that bounces is made of a natural rubber. The natural rubber polymer’s molecules are crossed linked by another substance. This prevents the molecules of rubber to slide past each other when a force is applied to the ball. When it makes contact with the ground, the ball flattens momentarily before bouncing back to its original shape. The upward energy created when it returns to its normal shape causes the entire ball to bounce upward again. The process repeats itself until the ball has no more energy and comes to a stop.

 

The no-bounce ball is made of butyl rubber. It acts just like the bouncing ball, except it absorbs more of the energy. The energy that makes the bounce ball bounce again is absorbed by butyl rubber, so it “dies” almost immediately. This is because there are no cross-links between the butyl rubber. When force is applied, the molecules in the ball slide past one another. The energy goes into deforming the ball. Butyl rubber is used as a shock absorber in materials such as motor mounts and inserts for running shoes.

 

When frozen, the balls reverse—that is, the ball that is supposed to bounce dies immediately and the ball that isn’t supposed to bounce bounces. The cold temperature slows the movement of molecules in each ball, thus reversing the characteristics. Let the balls return to room temperature, and they will behave as expected.

 

Conservation of Energy:

You should have noticed that the bouncing ball does not bounce higher than it was originally dropped. This is because of Conservation of Energy. This important law of physics states that energy is neither created nor destroyed, it only changes from one form to another. With the bouncing ball, the energy changes from potential energy (before it is dropped) to kinetic energy (while it is moving) to elastic potential energy (while in contact with the ground.) When the ball touches the ground, some of the energy is transferred to the ground. The ball therefore has less energy, and does not bounce as high. When the ball is thrown with some force, however, it gains energy from the floor and is able to bounce higher.

 

Fun Facts:

• Butyl rubber (as in the no-bounce ball) is used to make running shoes that absorb energy. This keeps the runners’ knees and ankles healthy by absorbing the joint-damaging shock of their feet hitting the ground.
• There are many kinds of materials that “remember” their original shape and return to it after being bent. There are metal shape-memory alloys (SMAs), shape-memory polymers (SMPs), and shape-memory ceramics (SMCs).
• SMAs are currently used commercially, particularly in new medical equipment.
• Vice Versa balls have been used as a magic trick for years.
• You can make your own bouncing balls in minutes.