Unbalanced logo

Important of Table Tennis Spin

. Is a spiral spin. If so, how? And if not, why not?

By Sagar ChedePublished 3 years ago 6 min read
Like

I play table tennis and we can hit balls to spin them in just about any way we can, except to spiral down its direction of travel like an American football throw. Sure, it could be fired from a rifled pistol to spin like this, but I'm wondering if it's even possible for a player with a normal paddle to achieve this result. It is quite clear that this cannot be done from a serve (zero spin), but it may be possible during the game to combine a particular incoming spin with a shot conferring another spin such as the net result. Is a spiral spin. If so, how? And if not, why not?

Here are the conditions of the problem: The ball is coming towards you. You can choose its speed and axis of rotation (if applicable) and speed of rotation. The only restriction is that the incoming axis of rotation cannot already be in the direction of flight. You must return the ball by hitting it anywhere on its surface with whatever force and direction you choose. Can you create a shot that causes the outgoing ball to spin sharply in its direction of flight? You can ignore gravity, air resistance, etc.

Certainly, you just need to rotate the paddle around the desired axis when you hit the ball. I guess this will have little effect on the bullet's flight path as there is no carioles force. When it hits the table, there will be an effect.

Don't worry about table effects, Carioles force, gravity, etc. The rotation of the paddle may give a slight twist but not a strong one. Also, I just added the condition that the incoming ball is not already spinning in its direction of travel.

It depends on how fast you spin your paddle, for example with a motor. The answer is that it is theoretically possible to rotate the paddle, but it may not be practical with a human arm and a standard paddle.

I think this might help modify the question to clarify something about the mechanics of spin production in table tennis. In particular, I think you can think of the racquet's contact with the ball as essentially instantaneous and the direction of movement of the racquet as in a straight line, in that the dwell time while the ball is in contact with the ball. Racquet is so short that a man cannot change the direction of movement of the paddle within this time. So responses like "spin the racket around the ball, maintain contact all the time" are not humanly possible.

This is called the spin of the corkscrew (alternatively the spin of the cork or the spin of the drill) - that is, a spin in which the axis of rotation is along the trajectory of the ball

The spin is given to the ball by hitting it with a glance. The very high friction between the ball and the rubber coating causes the ball to be very light along the face of the bat. To give a corkscrew effect, the racquet must be balanced perpendicular to the trajectory of the ball. However, to provide forward momentum, the racquet must simultaneously move parallel to the intended trajectory.

Both of these goals (turning the corkscrew and moving forward) cannot be achieved with a slicing stroke, especially if the ball bounces off the bat. But this can be achieved by rolling the bat forward around the ball in a "corkscrew" motion, imitating a bullet twisted out of a gun. The limited torsional capacity of the human wrist limits what can be achieved in practice to a compromise between a tight roll and a forward thrust, as seen at the start of this video. Because the thrust is applied parallel to the face of the bat, it necessarily introduces a spin in a perpendicular direction as well.

From what I've seen in this and other videos online, it seems virtually impossible to serve or return a ball with a simple turn of the corkscrew. A little side or back rotation seems inevitable.

It's a good answer and goes about as far as I am on my own, but doesn't seem definitive. Your argument about the need for a forward momentum is why I convinced myself that this is impossible from a static serve. High service is different and perhaps sufficient, but has no effect. It might seem possible if we choose the spin in, but it's too complex to see. I think a proof or a mathematical argument is needed.

Very good answer! I think the last paragraph is the key point here. It doesn't seem possible to serve with a simple corkscrew, as you have to give momentum forward. But it seems possible to serve some with a combination of corkscrew + side pin, and it might be possible to do it massively corkscrew (say 80% corkscrew + 20% side pin). I don't think the answer changes much if you hit someone else's blow; they would need an infeasible amount of support so you could hit purely under / over the ball and roll it back.

Just to clarify, when you say "static serve" you mean hitting the ball when it is at the top of its pure upward then downward trajectory i.e. when its speed is zero? If this is the case, yes, a rotation of the corkscrew is impossible from a static service: in general, the linear speed and the angular speed communicated by a single impulse are always perpendicular. This follows from the fact that, measured at the object's centre of mass, the force and torque are perpendicular, so the communicated linear / angular pulse is perpendicular, and a pulse is the limit of these things when the contact time becomes no.

Think of the static housing without gravity or air and a stationary bullet. Corkscrew shooting is impossible. The question is whether a specially prepared bullet not rotating on the desired axis can be struck at a special point of contact with a force vector resulting in the desired flight.

If the racket is allowed to be in contact with the ball for more than a moment, it seems pretty obvious that anything is possible. We therefore assume an ideal situation where the shots are instantaneous transfers of angular and angular momentum to a single point on the surface of the ball as shown.

The initial hit gives a linear pulse and an angular pulse perpendicular to the linear pulse. This perpendicularity results from the fact that the force is perpendicular to the torque, by definition of torque. So no, it is not possible to get corkscrew rotation (i.e. parallel linear and angular moments) in one shot from standing still.

Here's how to get it in 3 hits, however. Give player 1 a paddle with a certain amount of friction and give player 2 a paddle without friction. The ball starts motionless. Player 1 kicks the ball sideways. The ball now has non-zero linear velocity and non-zero angular velocity (perpendicular to linear velocity, as stated previously, although that doesn't matter for the rest of the argument). Player 2 gives it a hit that exactly cancels out linear velocity (and does nothing to angular velocity - player 2 can never change angular velocity since their paddle is frictionless). The ball now spins in place. Player 2 now hits the ball a second time, in the direction (or opposite) of the angular velocity. The balloon is now in the desired corkscrew path.

Note that Player 2's first stroke is actually a "negative" stroke - that is, Player 2 simply lets the ball hit his paddle while moving the paddle in the same direction, but slower than the paddle. ball; this is how to cancel linear speed.

The 3 moves can be upgraded to 2 as follows: just replace the two moves of player 2 with a single move whose linear impulse is the sum of the two linear impulses. Player 2's frictionless vane makes this simple.

culture
Like

About the Creator

Reader insights

Be the first to share your insights about this piece.

How does it work?

Add your insights

Comments

There are no comments for this story

Be the first to respond and start the conversation.

Sign in to comment

    Find us on social media

    Miscellaneous links

    • Explore
    • Contact
    • Privacy Policy
    • Terms of Use
    • Support

    © 2024 Creatd, Inc. All Rights Reserved.