Spinning the Ball
Get to know the scientific details of spinning the ball
Thursday, July 19, 2001
The spinning of the ball plays an important role in table tennis. There is spin almost in each stroke. Because of the sport nature and the equipment (rubbers etc), the spinning of the ball is inevitable. It has been found that the ball spinning in table tennis fluctuates from 0 to +140 rotational frequency (1/s).
Determinant factors of spin influence
The determinant factors which influence the spin of the ball are divided in: (a) external and (b) internal.
A. External factors
The main external factors are the following: a) The mass distribution of the ball and its surface properties. The largest part of the total ball mass is on its surface while its inside is empty. Table tennis ball has 19 mm radius, 0.4 mm thickness, and 2.5 gr weight. If we replace it with another ball of the same radius but with solid inside such as the golf ball, we will notice that the kinetic energy from the stroke can not be converted in spin. b) The type of the table surface and the floor material. These two elements influence a lot, the amount of spin and speed of the ball. c) The speed glue which used prior the match. d) The air resistance. The air decreases the amount of spin. Its action is proportional to the ball speed and the type of spin. e) The racket and the interaction of the ball with the rubber surface. The rubber material and the sponge influence the amount of spin. The offensive rubbers which are characterized for their ability to give more spin on the ball, satisfy at least two conditions: The amount of produced spin is proportional to the amount of friction between rubber and ball during the stroke. The kinetic energy, produced during the impact of the ball on the bat, is converted to spin and speed proportionally to the sponge thickness and rubber softness.
B. Internal factors
The amount of spin depends also on internal factors which are related to the point progression. The main internal factors are the following: a) The contact point between ball and racket and the degree of the formed angle. b) The speed of the stroke execution. The increase of the speed during the stroke execution is proportional to the amount of produced spin. c) The special conditions of the game. The possibility of giving greater spin on the ball with our stroke is theoritically proportional to the quickness of the ball coming from our opponent. d) The trajectory length of the ball during the stroke. The ball loses its spin because of speed reduction due to air resistance. This means that its trajectory length is conversely proportional to the amount of its spin.
© Dimosthenis Messinis
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