# Physics of table tennis

1. Sep 1, 2008

### kmikias

Most of the time i play table tennis and I always think about physics of table tennis .
My question is .
Is there any a very brief introduction to the mathematics and physics on table tennis?

2. Sep 1, 2008

3. Sep 1, 2008

### rcgldr

That web site wasn't very informative.

Here's a thread on top spin versus back spin countering:

Regarding this web page:

http://www.gregsttpages.com/articles/tt_physics_maths.html

Why a spinning and moving ball curves the air is called Magnus Force. There's dynamic versus static pressure, or Bernoulli effect. There's the more likely case of detached and turbulent air flow.

Bernoulli with mention of detachment (seperation) of turbulent air flow, top spin example:

http://en.wikipedia.org/wiki/Magnus_effect

Detachment of air flow (probably most of the reason for the curve):

http://www.geocities.com/k_achutarao/MAGNUS/magnus.html

More useful information such as elasticity (how much energy is preserved during a strike), for both linear and angular energy and how this effects various table tennis rubbers would be nice. For example, Mark V retains a lot of speed and spin energy during contact, while another rubber might retain a bit more speed, but less spin. The Mark V would be easier to block loops while at the table, because the returned ball would have more top spin and less speed.

If you drop a golf ball and table tennis ball in the air, the golf ball hits the ground first because it has a lot more weight (more force) and a bit less drag than the table tennis ball. I don't know what the point of this was.

One valid comparason between a golf ball and a table tennis ball would be the roughness of the surface. A rouger surface disrupts laminar flow sooner, and reduces Magnus effect, reducing how much the ball curves in the air, which is the purpose of the dimple on a golf ball. However, roughness is regulated by standards now, so you don't see the extremes of the 1970's where a Peace ball was very smooth, and a Barna was very rough.

The "powder" on table tennis balls should be wiped off before play, but if not, will end up on the rackets after a few rallies. The balls are replaced to reduce the chance of a ball breaking during play, which is different than the case for tennis (loss of pressure, and fuzz).
Off topic, but the amount of fuzz on tennis balls varies depending on the surface the ball is intended for (clay, grass, hard court).

The 38mm ball was faster because it's ratio of surface area to mass was less than a 40mm ball, so the 38mm ball was a bit less affected by drag, retaining a bit more speed, but less Magnus effect than the 40mm ball.