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.