Spin Angle and Friction in Table Tennis

Spin Angle and Friction in Table Tennis
Spin Angle and Friction in Table Tennis

The rotation of a table tennis ball after colliding with a hard surface is affected only by the angle of incidence and friction of the surface.

His ability to manage the ball's speed and spin on each return stroke helped the players competing in the World Table Tennis Championships finals secure their place in Sunday's games. Théophile Rémond of the University of Lyon in France and colleagues identified the variables that affect the spin rate of the ball bouncing off the table.

We refer to these variables as the friction of the hard surface and the angle of impact of the ball on the surface.

Rémond notes that the study is only concerned with the ball-table interaction because it only considers hard surfaces, ie non-deforming surfaces. Other determinants can play a role in the interaction of the ball and the racket, which is a soft surface.

For their experiment, the team threw a ping pong ball against a glass plate and changed the angle and velocity of the ball's strike. Then the speed of the ball, the rate of return and the recoil angle of the ball were determined using videos of the ball encountering the plate.

The team found that at angles of incidence below 45°, the ball rolled on the surface for only a small fraction of a full turn before bouncing, causing it to start spinning. The ball glided rather than rolled for wider angles of incidence, reducing recoil spin. When the researchers turned their attention to friction, they discovered that the amount of spin and the ball speed were both determined during the sliding phase and depended on the friction of the glass plate. As friction increased, the parameters saturated at levels determined by the rolling motion of the ball at small angles of incidence.

The researchers also discovered that the shape of the ball upon impact had no discernible function in the speed of the ball's rotation. Rémond finds this result intriguing, but doubts it will have any effect on how table tennis players perform.

Source: physics.aps.org/articles/v16/s78

📩 29/05/2023 14:57