This is a fun “magic” experiment to try outside, on the lawn, where your kids can spill as much water as they want to. It’s also nice to have grass under your table, so glass and ceramic dishes won’t break.
Since this can take practice, use old dishes and remind your kids to let you pick up anything that does get broken, so they don’t get cut! All you’ll need is a table, a sturdy, heavy glass that isn’t too tippy (we used a bar glass and it worked pretty well,) a smooth tablecloth and water. You can also try this with a heavy plate or bowl! Tablecloths without seams or old sheets with edge seams cut off work best!
We used easel paper as our tablecloth, but you can try a plastic tablecloth or a cloth one that doesn’t have a heavy seam on the edge. The more slippery the tablecloth, the better it will work. I’d also recommend bringing out a pitcher of water for refilling the glass and a towel for wiping up spills.
Put the paper or tablecloth near the edge of the table (see photo above.) Place the glass of water or plate on the tablecloth near the edge of the table. (I wouldn’t recommend filling your glass to the top.)
This part is important! You MUST pull the tablecloth straight down, along the edge of the table, very fast. If you pull it out, toward you, or pull it too slowly, it won’t work. If you do it correctly (and it may take a few attempts), the water will slosh a little, but the cup will remain on the table, full of water. We spilled a lot, but had a great time. All of the older kids involved were able to do it successfully by themselves, but I had to help my three year old a little.
The science? The law of inertia says that objects don’t want to change how fast they’re moving (or not moving, in the case of our glass.) They heavier something is, the more inertia it has. In our experiment, the heavy glass of water is standing still and doesn’t want to speed up. Since the tablecloth is moving under the glass very quickly, the heavy glass slips on it and doesn’t move very far. Even the friction between the glass and the tablecloth isn’t a strong enough force to make it move much. It seems like magic, but it’s just physics.
We did this experiment on Kare11 Morning news, if you want to see how it works!