The “Julia Child” of kids’ hands-on science
Here’s the first challenge: Bet another person can’t remove your hand from the top of your head. The challenge-taker must try to remove your hand according to your rules. Otherwise, it’s cheating. Sit on the floor. Place your hand with your fingers spread apart firmly on the top of your head. Have your friend grasp your lower arm next to your elbow. Now let him/her pull upward, trying to lift your hand from the top of your head.
Chances are excellent that you’ll be lifted off the ground before your palm parts from its perch.
Why is this so? If you’ve studied simple machines you may have learned about a mechanical advantage. That’s how a simple machine such as a lever can multiply your strength or speed. In this case, you’re putting your friend at a mechanical disadvantage. Your arm is a lever. In order to move your hand from the top of your head, you need an upward force near your hand. If that force is delivered as far away from your hand as possible, it loses its power. It’s easy to remove your hand if you deliver an upward force near your wrist. But at your elbow? No way! Got it?
Here’s another trick with the secret sauce of physics. Bet you can keep ten people from shoving you into a wall. Place your hands against a wall with your fingers spread and your arms outstretched. Have ten people line up behind you, hands on the shoulders of the person in front of them. At the count of three, have everyone push on the person in front of them as hard as they can. I mean, really lean in.
You, hero of the day, can hold them all off and not bend your elbows.
Why? Actually, each person absorbs the force of the person behind them so that you are not experiencing the cumulative force of ten people, only the force of the person directly behind you. So pick someone smaller than you to be that first person. If you’re not super strong, you can still be super smart.
If you don’t want to try this yourself, look at my videos of other people doing the challenges. Maybe you’ll change your mind.
If you like these bets, check out Vicki Cobb’s new release of We Dare You! You might want to join her We Dare You! National Video Project and make more videos yourself from her book. Learn more about it here.
Vicki Cobb is a member of iNK’s Authors on Call. You can invite her to your class through the magic of videoconferencing. Learn more about it here.
Tomorrow is Earth Day and Stephen Swinburne is going to encourage you to look up and down and all around you and really appreciate our planet.