Magnus Effect

Same effect that makes your drives slice to the right or hook to the left. Ball spin. The ball always travels in the direction of the spin.

That's why good golfers mostly want to put pure backspin on their golf shots. It's a thing of beauty, if you're a golfer.

Zip grooves chew the balls up too badly. Especially the Balata covers.

An easy way to demonstrate the Magnus Effect (if you can't make it to Hoover Dam) is to throw a beach ball with backspin. You can easily see the upward deflection.

Another easy way to demonstrate the effect is by making this simple toy.

You just need the cardboard tube from the middle of a toilet roll, some tape and an elastic band.

Make a "hook & grip" from the tape by folding it

and cutting a small notch,

and, stick it to the tube: you may need some extra tape to ensure it holds firm.

Launch the thing by holding the grip under the tube and "catapulting" it the way you would "fire" anything else with an elastic band:

Made with a cardboard tube like this they "behave" quite well: normally they'll curve upward 'til they stall then drop, but curve away again so that they "land" fairly flat.

But, if you experiment with longer smaller diameter tubes made from paper they can perform all sorts of acrobatics.

Don't expect any long flights though: I must try out a 2 litre drink bottle some time.