Literally from that link: "A ball with topspin bounces higher than a ball with slice."
Oh, well, that site seems pretty sketchy anyway. It wants to force download multiple files as soon as I load it.
FWIW here's Wikipedia: https://en.wikipedia.org/wiki/Topspin#Competitive_utility "On most court surfaces, topspin also makes the ball bounce higher. As a result, it is often used on clay or "soft" court surfaces which have a naturally higher bounce in order to make the ball harder for the opponent to hit. An opponent with a one-handed backhand is especially vulnerable to a topspin shot because it is difficult to hit a high ball with a one-handed backhand."
[EDIT:] Reading that sketchy site more closely, it appears to be a trick question:
> So, if you've been paying attention, you might say, "The question at the beginning of this article was a ruse?" Not exactly. In theory, it is possible to hit two balls, one with topspin and one with slice, that arrive with the same height. But in reality, that won’t happen. You have to hit a slice low over the net, otherwise it will fly long. On the other hand, you want to hit a topspin-ball high over the net; otherwise it will land short or in the net.
What makes all the difference in tennis is that topspin and backspin shots go over the net at entirely different angles. You're not just hitting a flat shot with spin.
tennis: https://tennisone.tennisplayer.net/club/lessons/inen/bounce2...
pickleball: http://applecountrypickleball.blogspot.com/2015/12/spin.html
table tennis: https://www.allabouttabletennis.com/table-tennis-techniques-...
edit:
ok now I am very confused, as I can also find reports of the opposite effect, for example:
https://blog.tennisplaza.com/spin-effect-the-physics-behind-...
Can anyone explain why topspin makes a ball bounce lower (matching my experience and some online reports) and also higher (matching some reports in this thread and online)?
All else being equal, both can't be right. So is there some other variable at play, such as velocity, surface coefficient of friction, etc? Or is someone wrong?