Water scooters are simple toys that effectively demonstrate the principle of surface tension. Here's how to make them:
A water scooter is nothing more than a small piece of waxed paper cut in the shape of a rocket with a channel cut into its rear end. Fill a large pan with water, place the scooter at one end and touch a skewer that's had its end dipped in liquid soap into the rear channel and the scooter will shoot forward.
What's happening is that the drop of soap suddenly reduces the surface tension of the water in the channel. The water is then free to expand out of the channel, pushing the scooter forward.
The one problem with this demonstration is that the small amount of soap introduced into the pan is enough to eliminate the surface tension over the entire surface, so a second attempt to make the scooter scoot will fail. To repeat the experiment, it's necessary to rinse the pan and replace the water.
That limitation not withstanding, this is still an interesting and entertaining experiment.
There is no limit to the shapes given to the scooters. For example, the following is a 3D scooter made out of aluminum foil:
Please click on the following YouTube video for a live action version of this page:
Return to my main page to browse 60 other subjects