Have you ever wondered why it’s so hard to get ketchup flowing out of a bottle, or why no-drip paint doesn’t drip?
Ketchup, no drip paint, liquid soaps and shampoos are all part of a really amazing category of fluids known as “shearing liquids.” These fluids are pretty thick when they’re sitting still, but they get thinner or more “liquidy” as they flow, because movement decreases their viscosity, or thickness, making them more slippery.
Back in 1963, an engineer named Arthur Kaye noticed streams of liquid shooting from the surface below a stream of shearing liquid he was working with. This strange, short-lived phenomena became known as the Kaye effect.
With a chair, tape, some dish soap and a plastic ziplock bag, you can do your own Kaye effect experiment at home and watch soap jets shoot like ski jumpers from the very slippery shearing liquid soap pile below
-Tape a plastic ziplock bag to a chair with one corner or the bag pointed toward a plate underneath. The bag corner nearest the floor should be around 20 cm (about a foot) from the floor.
-Fill the bag with liquid soap or dish detergent. We added a few drops of food coloring to ours.
-Cut off the corner of the bag closest to the floor with scissors to make a tiny hole for the soap to flow through (1mm.) You may have to make it a little bigger, but you want a very thin, steady stream of soap flowing to the plate.
-Watch for jumping streams of soap. If it’s not working, try changing soap and adjusting bag hole size and bag height! What happens if you put the plate below at an angle?
To learn more about the Kaye effect and other cool physics stuff, visit Dr. Skyskulls’ website. He’s the physicist who told me about this experiment and helped me work out the protocol.
It’s getting nice outside. Time to start thinking about backyard science! Here’s one of our favorites, if you haven’t already tried it! We threw eggs on Kare11 Morning News last spring. It was pretty funny…and messy!
“Kids aren’t getting dirty these days. They’re not playing in the mud, not playing in rain puddles,” says Dr. Truglio, of Sesame Workshop in a Wall Street Journal article, about getting your kids outside.
Next to the kitchen table, my back yard (or front yard) is my favorite science laboratory. It has the added bonus of being easy to clean up. For this fun, messy experiment, a hose and a few paper towels do the trick. Make your kids clean up whatever mess they make!
My dad, who is a physicist, told me about this great demonstration. It teaches kids a little bit about motion and force while letting them do something that they are rarely, if ever, allowed to do- throw eggs! All you need is a sheet, some clothespins or string, raw eggs, and some paper. (You could use newspaper or easel paper. It is just to make cleaning up easier.) I also used a portable table turned on its side as a wall, but you could just use a wall or the side of a garage and have your child hose it off when you are finished.
Hang the sheet up from a tree, if you have one. If you don’t have a tree, you could hang it from anything else, or have two tall children or adults hold it. Then have two kids hold the bottom of the sheet up, or tie it to chairs so it makes a J shape when you view it from the side. The idea is to keep the eggs from hitting the ground and breaking.
An object in motion wants to remain in motion. To stop an egg moving through the air, you have to apply force to the egg. In this case, the force will be applied by a hanging sheet, or a wall.
Throw a raw egg at the sheet as hard as you can. It won’t break because the sheet slows the movement of the egg as it comes to a stop. The law of motion says that the faster you change the speed of an object, the greater the force applied to the object will be. When you change the speed of the egg slowly, like the sheet does, it lessens the force applied to the egg and the egg remains intact.
Now, put some paper on a wall (or table like we did.) Throw an egg at the wall. You’ll see what happens when something stops fast. Once again, the law of motion rules. When you change the speed of the egg quickly, it stops with a lot of force. SPLAT. This is my kids’ favorite part.
This is why they put airbags in cars. If a car is moving and hits something, causing it to stop very quickly, the airbag act like the sheet, slowing the person in the car down SLOWLY and greatly reducing the amount of force they might hit the dashboard with.
Record your results in your science notebook, if you want to. Finally, be sure to wash your hands when you’re finished experimenting and cleaning up. Raw eggs can have bacteria called Salmonella living in them and on them. Have fun!
When my 6-YO and her buddy asked whether they could make slingshots this morning, so they could shoot stuffed animals at a tower of blocks, I couldn’t say no. It’s physics after all. A few months ago, my kids had a great time making slingshots with their plush Angry Birds, as you can see in this video.
We got out a chair, some rubber bands, and a plastic ring like the ones they put on prescription bottles. Within minutes, they were laughing hysterically while stuffed bunnies flew through the air. Click here for detailed directions on how to make the slingshots and to learn more about slingshot physics.
My kids brought “Angry Birds” to life this morning by making Marshmallow Slingshots and using them to launch their Angry Birds stuffed animals at a tower of blocks (with a stuffed pig on top, of course.)
To make your own angry birds slingshot, all you need is a chair, some rubber bands, and a plastic ring like the ones they put on prescription bottles. Click here for directions and to learn more about slingshot physics.
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!
Now that it’s summer, move your science lab outside and try doing the Tablecloth Trick or Throwing Eggs. If you’d rather check out the power of the sun, try making a solar oven from a pizza box! You probably have everything you need for these experiments right in your kitchen, and if you don’t have a pizza box, just save one next time you order out.
What are you waiting for? Have fun!