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Saturday, June 18, 2022

Keeping the Ball from Going Long When Hitting from the Kitchen Line

 It's time for a bit of calculations.  Let's stroll back to those physics classes in which I wish I'd done better.  

Imagine that you are standing at the kitchen line and you want to hit the hardest shot possible and keep in inside the court.  We will make some assumptions here, one being that you will hit it over the middle of the net, which is the lowest point and thus has the most likelihood of landing in.

I'll bring up gravity and spin in a moment, but consider a ball at top of net height.  If you look at the angles, there is no path for the ball to land in the court unless the ball was hit from a height of 44.8 inches, or 11 inches above the net.   Think of a laser pointer that just clears the net and lands on the base line or just goes long and then you raise the pointer until it hits the baseline.  I used a tangent calculation to get the 44.8 inches -- I have no laser pointer anymore. it's a long sad story.

If you are going to hit the ball hard and spinless and it's not very high above the net, it's unlikely to succeed.

Gravity: I'm guessing a bit on hang time here, but a shot hit from the kitchen line might hang somewhere between 0.25 seconds and 0.5 seconds.  I've noticed that the time for a shot and then a return is about a second.  More time if hit softer, less when smashed, this shortens as players more closer together and/or hit the ball harder..

In 0.25 seconds a ball will drop about 1 feet, and in 0.5 seconds, the drop is about 3 feet.  So the slower you hit the ball, the more likely it will drop in.  One more reason to never overhit a ball.

Spin: top spin will help drag the ball down and a cut spin will cause it to stay in the air longer.  I'm not real sure about how to calculate that and since spin varies a lot, and wind is big deal since the ball is very light, it seems there may be a lot of important variables yet in play.  Where is Bernoulli when you need him?  Actually there are probably equations there, but I'd need a lot more data to figure it out.  Well, I just looked a bit and it seems that no one has calculated the total drop per rpm or something like that.  However, top spin is a great friend to have when trying to keep a ball from going long.

Also the ball is slowing down because it is so light. As we saw above the slower ball will drop more than a faster ball.

So how does this help us play better?  I was surprised by how high you need to have the ball to keep it in.  I tend to speed up balls that are at net height and even a bit below.  This seems to work with my backhand roll better than my forehand.  It is a slow ball with lots of spin, the best of both worlds.  (It also tends to change the pace of the point, but tempo is a subject for another post!)

If you hit the ball from a lower position, you are going to have to do something.   Note that you will need to initially hit the ball up to clear the net and then to keep it in we need spin or gravity.  Adding to that are the opponents who will gladly counter shots that are above the net on their side.  The PB problem in a nut shell: get it up, but not too far up...

If we ran the numbers, I would suggest that marginal shots should be dinked back.  When in doubt, dink.  Get them over the net and reasonably shallow.  Wait for a higher ball to not dink.  (OK, if you want to lob, fine, just go ahead, I don't care...  ;-))  If you hit the marginal shot, you will be fine if you can get it past an opponent or more likely, hit it right at them.  The dominate side hip to shoulder is a traditional target for that shot.  And to keep the ball in at a reasonable pace, you need to hit a top spin shot.  If you are going for a body shot, then hit it hard and flat, don't worry about keeping it in.

There are players who use little top spin and are effective at the net.  They hit the ball very flat and it can be hard to handle.  Top spin shots have more arc to their trajectory and if they are not good shots are easily countered with a block or counter hit.  The flat shots are awkward, but they will go long if not done well.  If you are playing against the flat shot people think about letting some of the shots go by.  

This all seems a bit disjointed, but I'm getting tired of it.  It's been through a number of revisions.  Let's boil it down to these points: Don't speed up a ball that is below the net, Learn to spin your ball, think body shots, when in doubt dink!  Oh, and "Lob if you must."

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