Section 1: How to strike ball with accuracy
The rules of Table Tennis stated that, when a ball that is legally played, bounces on a playerís side of the table, the receiving player must return the ball to the opponentís side of the table before it bounces a second time, without sending it off the table or into the net. This rule show when competing, a player who legally returns the ball with greater accuracy would have the better chance of winning points and winning the game. The opposite would be true, if a playerís return percentage is lower than that of the opponent.
The research into how to strike ball with accuracy begins with looking into the formation of flight trajectory. On a table that measures 275cm X 152cm, stands in the middle a 12.25cm high net. When striking a ball, a player must return the ball onto the opponentís side of the table regardless of the oncoming ballís placement, near or far from the net, high or low bounce and type of spin. This is the point for our investigation into how to strike ball with accuracy.
If we closely observe the flight path of a Table Tennis ball when two players are playing each other, it is not different to see that balls landing on the table that have no curvature (straight line) in its flight path (see diagram 1), are for less than balls landing on the table that have a curvature in its flight path (trajectory).† The reason for this is only when the oncoming ballís placement is farther from the net and has a lower bounce, then you must create a suitable curvature in the flight path so as to avoid hitting the net or sending the ball off the table (see diagram 2), and thereby achieve a high return percentage. The trajectory of a Table Tennis ball in flight is formed by the maximum height of the curve and the distance travelled.
†††††††††††††††††††† †††† Diagram 2††††††††††††††††††††††††††††††††††††††††††††††††††† Diagram 1
2: Maximum height of trajectory (MHT), represent the highest point of the flight path of ball, and the distance travelled (DT) is represented by the distance between the point of contact by playerís bat and the point at which the ball lands (see diagram 3).
The force of gravity produces the ball trajectory, pulling it to the ground, and the Air resistance.
†††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††† Distance Travelled (DT)
The trajectory of the ball is also depend on the direction of the force applied when the ball is struck, the angle of the bat at the time of impact, the amount of force exerted onto the ball, the type of spin imparted on the ball, and the characteristic of the oncoming ball.
3: Direction of force and its impact on trajectory
At the time of impact, the direction of force is the same as the direction of bat travelled. It could be travelling forward, forward and upward, or forward and downward. Different direction of force creates different height of trajectory (MHT) and distance† (DT).
The example given below will help us to understand the relationship between the height of trajectory (MHT) and distance (DT).
††††††††††††††††† Diagram 4
This is the type of force you should create when practicing the Kill or Downward Chop.
3: The angle of bat
When striking the ball, the point of contact will vary according to the different bat angle. The bat may make contact with the top of the ball, bottom of the ball, middle of the ball, and between top middle or bottom middle of the ball, etc.
The different contact points create different heights of trajectory and different lengths in DT. For example:
When the same amount of force is applied in the same direction, a closed bat angle would make contact with the upper part of the ball. This would lower the MHT and reduces the length of DT of the ball. The closer the bat angle the lower the MHT and shorter the DT.
†††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††† Direction of Force
As practical experience correspond support these principles, we may therefore conclude that: when oncoming ball bounces higher than the net, or when the oncoming ball is taken on the upward bounce and when oncoming ball is heavily topspin, the bat should be closed or very closed in order to lower the MHT and shorten the DT.
This action would compensate for the upward catapult effect and therefore prevent the ball from going long or out.
This is the method to use when killing a ball that bounces high near the net.
When the ball bounces lower than the net, and is heavily backspin, or when the oncoming ball is taken on the downward drop, the angle of bat should be opened or very open. That would rise the MHT and lengthen the DT, and would compensate for the downward catapult effect, preventing the ball to go into the net. This is the method to use when making a slow push or chopping a low bounced ball.
When the oncoming ball bounces lower than the net or when the ball is taken below the height of the table, the bat should not be too opened if you desire to attack the ball, because the ball may go into the net. The point of contact should be middle top with an upward force added to increase the maximum height of trajectory and thus avoid sending the ball into the net.
When the oncoming ball bounces higher than the net, the bat angle should not be opened too much when chopping, as the ball would go long otherwise. The point of contact should be middle bottom, and a downward force added to lower the MHT and prevent the ball going out.
4: Effect of force variation on trajectory
The amount of force that has been put on the ball varies the acceleration of the ball on its flight path. Greater the force, greater the speed. Lesser the force, lesser the speed. The speed of the ball affects the trajectory as well. For example:
A: When the force applied is a constant upward and forward force, the ball would travel faster when hit with greater force. This also increases the maximum height of trajectory, and lengthens the distance DT. On the other hand, the ball would travel slower when it is hit with a lesser force. This also lower the MHT, and shorten the DT.
Practical experience and these principle shows, when the oncoming ball is far from the net and bounces low, it should be hit with increased force. This increasing ball speed would result in higher MHT and lengthen the DT, so as to ensure adequate height and length of return. This is the method to use when playing attacking shots away from the table and chopping balls away from the table.
When an oncoming ball is near the net, and bounces lower than the net, it should be hit with lesser force. This decrease the ball speed to suitably lower the MHT to clear the net, and the distance DT, so as to ensure that the ball does not go long. This is the method to use when making high loops near the table, lifting balls near the net, making blocks, chopping a low and short ball and playing drop shots.
B: when the distance DT is constant, if the force is greater, then the ball speed is faster but the MHT will be lower. The weaker the force, the slower the ball speed but the MHT will increase.
The practical experience and these principles shows that, if greater force is used to lower the MHT and shorten the DT, it would work with reasonable success only if the oncoming ball is near the net and high. Should the oncoming ball bounce at net-high or lower, the success rate would be much lower, or even to a point where the ball would not make it onto the opponentís table.
If we use lesser force to higher the trajectory and shorten the distance DT, it would increase the success rate but because of the returnís slower speed and higher bounce, it gives easy opportunity for the opponent to attack. This is the reason why flat hit or lift and drive (produce little or no spin on the ball when hitting it) is not advisable to be used.
5: The effect of different spin on trajectory
When hitting a ball if you produce spin (top, bottom, side, etc.) upon it, it would affect the trajectory.
The effect of Topspin and Backspin on trajectory:
A: When the direction of force is constant, if Topspin is introduced onto the ball, it would lower the MHT and shorten the distance DT. The stronger the Topspin the lower the MHT.
If Backspin were produced, it would lengthen the distance DT and increase the MHT.
The stronger the Backspin, the higher the MHT, so much that it would even cause a inverted trajectory or the ball coming back on itself.
B: When the distance DT is constant, if the ball is hit with a certain amount of Topspin the MHT must be suitably raised so the ball cleans the net. The stronger the Topspin, the higher you need to raise the MHT to compensate for the suppression of MHT by Topspin. On the other hand, if the ball is hit with a certain amount of Backspin, the MHT must be suitably lowered to compensate for the amplification of trajectory by Backspin.
The greater the Backspin the more we need to lower the height of trajectory.
These principles, together with point of contact and bat angle, have different impact on trajectory.
How to make use of Spin to alter the line of trajectory in relation to improving Accuracy:
As mentioned before, it would be most beneficial if attacking shots were hit with a certain amount of Topspin, because it creates better trajectory and greater speed. What is more important, this greatly improve Accuracy, because it achieves a higher rate of good returns against near the net balls and below the net balls as Topspin helps to alter and heighten trajectory so the ball could clear the net, and the same time shorten and manipulate the distance DT for added control.
Many players make strong loops or compact light Topspin shots with higher ball trajectory but shorter distance DT, and achieve a high rate of accuracy by making a good use of the impact of Topspin.
Many fast-attacking players often hit the ball flat and without Topspin, which means they have to lower the flight path to shorten the distance DT. This method has a reasonable success rate against balls that bounce higher than the net, but are much less successful against balls that bounce lower than the net.
If Friction introduced against ball when flat hitting to create a small amount of Topspin, it would create more trajectories and therefore improve accuracy.
On the other hand, hitting a ball with Backspin is not conductive towards creating a better trajectory or greater speed. Choppers therefore have to raise the maximum height of trajectory enough to get the necessary height for the net clearance when they play balls near the net or balls that bounce lower than the net, and the same time, reduce the ball speed to shorten the distance DT, so as to prevent the ball from going into the net or long.
Through the analysis it can be conclude, that Trajectory and Flight-path and their variations are highly complex. Before we can decide how to make a return, we need to consider how far away the ball is from the net, the height of bounce (high or low), the type of spin on the ball, and whether it is to be taken with early or late timing.
When we actually make the return, we need to pay attention to the collective impact on trajectory created by the direction of force, the bat angle, the amount of force and spin, and the nature of the oncoming ball so as to create an appropriate trajectory for the return and therefore achieve greater accuracy.
Considering the fact that attacking shots and defending shots have different demands on direction of force and bat angle, as well as the different impact the two spins make.
There are basic differences in the method for creating trajectory when playing these too types of shots:
A: Attacking shots (including fast attacking and looping shots) and production of trajectory.
A: When the oncoming ball is near the net and high, trajectory is less important, as long as we take the appropriate point of contact (middle top) and apply forward and downward force for this situation, we may easily attain good accuracy.
B: When the oncoming ball is far from the net and high, then a certain MHT must be created for the trajectory and, the DT must be suitably shortened. To do so we must take the correct point of contact (Middle Top) and apply forward and a little upward force. We should introduce a degree of Friction to create a certain amount of Topspin so as to suitably raise the MHT and shorten the DT. This is the way to improve Accuracy in this situation.
C: When the oncoming ball is far from the net and low, then we need to raise the height of trajectory and suitably lengthen the distance DT, the point of contact should be middle or middle top. Direction of force should be forward and upward, and to increase the amount of force to avoid the ball going into the net.
D: When the on coming ball is near the net and low, we need to create a higher MHT and shorten the DT. The point of contact should be Middle Top and the direction of force should be upward and forward, and introduce Friction to impart a certain amount of Topspin so as to avoid playing the ball long. The near the ball is to the net, the lesser the amount of force should be so as to shorten the DT.
E: When the oncoming ball carries strong Topspin, we must pay attention to lower the MHT for the purpose of shortening the DT. The point of contact should be Middle Top or even Near Top and direction of force should be Forward or Forward and Downward, and to suitably increase the amount of force when playing the shot to prevent to ball going long (the stronger the oncoming Topspin the greater the amount of force when making the Return).
F: When the oncoming ball carries strong Backspin, we must pay attention to raising the MHT for the purpose of lengthening the DT. The point of contact should be Middle or Middle Bottom. Direction of force should be upward and forward, and to suitably increase the amount of force when playing the shot to prevent to ball going into the net (the stronger the oncoming Backspin, the greater the amount of force when making the Return).
A: When the ball is near the net and high, trajectory is less important. As long as we take the correct point of contact (Middle or Middle bottom) and apply an Downward and Forward force, the ball would then travel with a trajectory of a near straight line or inverse curve to land on the opponentís side of the table.
B: When the oncoming ball is far from the net and high, we must pay attention to lowering the MHT for the purpose of shortening the DT. When playing this Chop Return, the point of contact should be Middle Bottom. The direction of force should be Downward pressing and forward so as to prevent the ball from going high and long.
C: When the oncoming ball is near the net and low, we need to raise the MHT and shorten the DT. When playing the Chop return, the point of contact should be near bottom. The direction of force should be forward and without downward force. A little amount of force should be used to reduce the speed of the return so as to avoid sending the ball into the net or long.
D: When the oncoming ball bears strong Topspin, we must lower the MHT for the purpose of shortening the DT. When playing Chop return, reduce the angle of your bat backwardly-inclines. Pint of contact should be Middle bottom, and increase downward force to cancel and compensate for the Topspin on the ball (the stronger the oncoming topspin, the greater the amount of force when making the return), and prevent it from going high and long.
E: When the oncoming ball carries strong backspin, we must raise the MHT for the purpose of lengthening the DT. When playing this Chop return, increase the angle of the bat backwardly-inclines. Point of the contact should be near bottom, and increase the forward force to cancel and compensate for the backspin on the ball to prevent it from going into the net.†††