Why does the tennis ball speed up after it bounces?

Question

My buddy and I were playing tennis tonight and he remarked that the tennis ball seems to speed up after it bounces after I hit a hard forehand. He was wondering how I did that so that he can start hitting them too. I told him that I really didn't know what I was doing differently from him.

I've seen this phenomenon as well occasionally when I play against some hard hitting opponents and I was wondering what makes it speed up. I know that I'm hitting my forehands fairly flat with slight side spin and I'm hitting it pretty hard. We're also playing on American Hard courts.

Thanks in advance for the answers, and yes, I will choose a best answer!

Answer 1

Because when you hit the ball that way it gives it a forward spin.  That spin is far less affected by air friction than the forward movement of the ball through the air.  So when the ball hits the ground it has slowed some due to drag from the air but is still spinning quickly.  That spin gives it an extra forward boost when it hits the ground and speeds it up. (Which also slows or stops the spin)

Answer 2

the above answer is correct, also you might try considering that on a hot day the tennis ball will bounce up higher thus it may appear to be going faster

Answer 3

The ball doesn't speed up after it bounces it just seems that way. It is physically impossible for the ball the speed up after it hits the court because energy is being expended when it bounces. For it to speed up more energy would have to be applied to the ball, not lost.

Answer 4

Both of the other answers are both correct but not quite.  When hitting in tennis it is clearly impossible for the ball to speed up after the bounce.  In fact, the balls slows significantly when it bounces.  However, when a ball is hit with increased spin the bouncing ball reacts accordingly.  When you slice a ball the backward rotation slows the ball more than a normal rally shot making the ball seem to almost stop in the air and fall down.  The opposite can be said for a topspin shot.  The spin will actually change the angle of the ball making it bounce up higher than usual and decreasing the amount that the ball slows upon impact with the court.

So when a ball appears to speed up its because it is hit with topspin and it makes the ball react differently with a higher bounce which gives the sensation of it speeding up when trying to hit it.