5 Minute STEM Activity 2 - The Floating Arm Trick

I've drafted a few 5 minute simple STEM activity posts and I'll share them with you over the next few weeks of the Summer holiday. These 5 minute activities are designed to make your children think and learn about what makes up their world. None of them require anything complicated or any scientific qualifications, and if you want to learn more - you have the Internet and the entire knowledge of the world, right there in front of you...

The Floating Arm Trick.

You don't need any equipment other than yourself and a flat wall. A closed door works perfectly.

1. Lean hard against a wall and press with your whole arm and the back of your hand, but not your body.
2. Press hard against the wall for 30 seconds. You can count in bananas or potatoes, elephants or mississippi if you aren't sure how long a second is.
3. Step away from the wall with your arms by your sides and relax. What happens to your arm?

Why do you think this happens? What were the muscles in your arm doing before? What are they doing now?

Scientists call this the Kohnstamm phenomenon, or "The Floating Arm Trick". 

After telling your body to do something for a while - a voluntary action - your body tries to predict what you want to do, automatically take over and continue doing it for you - an involuntary action. In this case, it's not necessary, but we are very pleased our eyes carry on blinking when we get distracted!

You can find the first 5 Minute STEM Activity here - Fish In The Tank
and all of the 5 Minute STEM Activities here...