bounce

[saraho]

what makes a table tennis ball bounce?

[stevie21]

Bouncebackability

[Space]

you might get better answers if you post in the "Science" section

[fo3nix]

well anything bounces due to gravity, newton's laws etc. but i suspect the question is more to do with why does a table tennis ball bounce so highly, compared to say a normal tennis ball.

to this, i think it's just the fact that the table tennis ball is very, very light. it's also made of a material that doesn't compress much.

if you have something that compresses easily, and thus absorbs energy easily, such as blue-tac or something, then it wont bounce that highly as any energy it built up while being dropped to the floor is used to change the shape of itself while hitting the ground (even if you cant see it changing shape as it happens so fast). but with a table tennis ball, the plastic it's made from won't compress as easily, and thus more of the energy it's accumulated while being dropped can go into bouncing the ball back up. seems a sensible theory to me anyway..

[Jay70]

Don't things bounce when they are overcoming gravity after intially being attracted by gravity? 

[Space]

I don't think it's got anything to do with weight, since rubber balls bounce just as well...
I think it's just the material. Some materials will dissipate and waste a lot of energy on impact, so there isnt much energy left to bounce back up,
other materials will store nearly all the energy as they get compressed, and give it back as they go back to their initial shape, giving the ball momentum to bounce back up.

[chazza55]

The previous posts are all correct to some degree. I can throw a little more light on the subject, but neither do I claim to have the full story:

If a body falls and makes contact with a surface, Newton's 2nd law states that the impacting body will experience an equal and opposite reaction. (conservation of momentum)

So the ball will experience a force relative to the speed the ball impacted at, and the mass of the ball.

F=ma

Energy must be conserved. It cannot be created or destroyed. A negligible amount of energy will be dissipated by the sound of the impact, another neglible amount by the heating of the surfaces due to flexing etc.

This brings us to the material of the surfaces in contact. The "coefficient of restitution" is a measure of how elastic a surface is.

The more elastic the surface, the more kinetic energy will be absorbed by the material. Thus less energy to provide velocity in the other direction.

So my answer (sorry for the long post) is THE "COEFFICIENT OF RESTITUTION" and "Newton's 2nd Law"

look them up and you may find more answers.

Hope that helps.

[Clanad]

Not that it matters much to this discussion, but ping pong balls are made from celluloid, not plastic...

[Gef]

Clanad, celluloid is a thermoplastic material. Plastic is not the name of a substance but a description of its properties.

[Gef]

Some really confusing answers here. For an object to bounce surely either it, or the surface it hits, must be able to deform and then be able to regain its original shape. Shperes (balls) seem to be better than other shapes. The height of the bounce will depend on lots of factors - speed at impact, mass of ball, type of surface etc.

[Clanad]

Gef, you are certainly adept at the picking of nits...Plastics are relatively stiff materials made of polymers (long molecules made of smaller molecular units joined together) and other ingredients such as fillers, pigments(for color), plasticizers, flow improvers, and stabilizers. On the other hand, celluloid is the name of a class of compounds created from nitrocellulose and camphor, plus dyes and other agents first invented in 1848.  Granted, a general term is thermoplastic, however in the context of fo3nix's statement, mine was for clarification purposes only, not argument...