Inside: Dynamic and creative activities for hands-on exploration of Newton’s 3rd Law of Motion. Try our twisting challenges during commercials as you watch the Summer Olympics this year.
The Summer Olympics are coming up! Are you excited? What’s your favorite sport to watch? Since all my kids are gymnasts, for us, it’s gymnastics.
One thing I like to stress to my kids is that a great athlete is not just a dedicated person with a strong body, good coordination, and body/mind control. It’s someone who understands the sports science, and the physics of movement, and can use that knowledge to his or her advantage.
Many aspects of physics can be covered using gymnastics – energy, force, and friction – but today, I want to concentrate on twisting.
Newton’s Third Law of Motion
To understand twisting, one has to start with Newton’s 3rd law of motion: for every action, there is an equal and opposite reaction. The harder a gymnast pushes against the beam, the higher her lift is into the air. Any time you want an upward movement, you have to start with a downward push. The “down” and “up” are two equal forces working in opposite directions.
The concept of “equal” was hard for my kids to grasp at first. When I told them that they exert a force on a ball (called action) by kicking a ball, they nodded their heads. It made perfect sense. But when I told them that the ball exerts an equal force on their foot called reaction, they protested.
How can it be true?! The ball is doing no such thing!
Here’s the thing, it’s true. If the ball didn’t exert the force on your foot, you wouldn’t even feel it when you kicked the ball. You can feel the force of the ball in the compression on your foot at the moment of impact or connection between the ball and your foot.
The physics of twisting is taught in college-level mechanic courses, but as Albert Einstein said, if you can’t explain it simply, you don’t understand it well enough.
In preparation for the Olympics, I thought it would be fun to do a couple of hands-on activities that demonstrate the concept of twisting to my little kids in a simple way. We started by watching the twisting of a falling cat through videos on the internet. Second, we used the power of water to twist a can of soda. And finally, we watched women’s gymnastics from the last Olympics and used our bodies to practice twisting.
Do Falling Cats Defy The Laws of Physics?
Until the camera was invented, scientists had a hard time explaining how cats manage to land on their feet without defying the laws of physics. (If you are curious, here is the first-ever cat video made in 1894). How can cats possibly manage to turn in the air, with the absence of force giving it an initial rotation?
Newton’s 3rd law of motion specifically states that there must be two equal forces working in opposite directions, and the only forces working on a falling cat are gravity and friction. How can a cat use these forces to turn?
Physicists analyzed falling cats and discovered that all falling cats perform the same nifty trick. As they fall, (1) they bend in the middle to create two different axes of rotation: that is, the front half of their body rotates about a different axis than the rear half. (2) They turn in the front legs while leaving the back legs extended. The result is that the front and back of their bodies start rotating in opposite directions creating their own rotational force.
In short, by rotating sections of their body in opposite directions, cats manage to move their body as a whole. (It also helps that cats do not have a collar bone and turn their heads 180 degrees to look down as they fall).
I made my kids a toilet paper roll cat to help my kids understand the concept of axis and how rotation happens. The body consists of two rolls so “the cat” can rotate the front and the rear parts in opposite directions like the real cat. I put some stripes on the back of our cat to make the rotation more evident. If you don’t like the idea of your cat being so unnaturally long, just cut one paper roll in half and use that.
Twisting Soda Can Experiment
We made a can twist in this experiment by strategically placing holes along its bottom to harness the gravitational force. The created rotational force surprised and fascinated my kids to no end. Twisting Soda Can is a great outside experiment for summer.
Hands-on Twisting Fun for Kids
Did you ever wonder why gymnasts do cartwheels before going into a backflip? A cartwheel is a twisting force that tends to cause rotation!
Ask kids what some other things that help us twist our bodies are?
How about the position of our hands? Ask kids to spin in one place while keeping their hands straight down by their bodies. How did it go? Now ask them to spin while spreading hands to the side? Which position of their hands creates better spinning? Hands out or hands down?
Look at this video of a gymnast performing her vault routine in slow motion. Doesn’t she seem to defy all the rules of physics by staying in the air so incredibly long with no apparent force to hold her there? More time in the air means more time to complete somersaults. And how does she get more time in the air? By jumping down as hard as possible to spring high into the air.
The kids really enjoyed watching this long video. There are many nice slow-motion sequences.
After watching gymnasts perform, we decided to create a series of twisting challenges by changing variables to see if we could produce better twisting without special equipment.
Remember how the upward movement is created by downward push? We decided to vary how hard we jump on a pillow to see if it will change how much we can twist.
(Safety note: make sure the kids are jumping on a soft surface like grass or carpet, and the carpet is securely attached to the floor. Make sure the pillow is not covered with slippery material like silk).
- Stand on one end of your working space with a pillow about a foot or two in front of you.
- Start running and then jump on the pillow with some force.
- Immediately jump off the other end, trying to twist the body 180 degrees in the air.
- Now see if you can perform a 360 degrees rotation.
- Try this a couple of times.
My kids couldn’t get enough of this experiment.
- Stand in front of a pillow.
- Jump on the pillow and immediately jump off, trying to twist the body 180 degrees. Then 360 degrees.
- Try this a couple of times.
Which position of the pillow allowed for better twists?
Now try varying the position of arms: swinging arms, extended straight overhead, straight out to the sides, glued to the body, etc. Would jumping on one leg allow for better twists? Or maybe try shoes and no shoes?
Summer Olympics Freebies!!!
I made you a 20-page printable that includes fun facts about the games, an Olympic Games scavenger hunt, maze, riddles, Olympic Games Challenge, coloring pages, some math, language arts, and of course, a crossword puzzle, word scrambles, and word searches. Enjoy!
Are you looking for more Olympic-related activities, crafts, and books to explore with your kids? Click here for inspiration from the best kid bloggers from around the world. And for extra fun, try an Olympics Challenge for Kids that you can print off kcedventures blog.
What are your favorite Olympic sports?