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Freeze Frame


You and Your Students!

Script By

Vicki Cobb, Education World Science Editor


Bet you can’t hold your hand still!


Human Body

Required Props

  • a table knife
  • a wire paper clip

Setting the Scene (Background)

Do your students like to play the game "Freeze?" I'll bet they haven't noticed that the harder they try to remain still, the harder it is. Small motions are especially hard to control. Here's a bet no one can win: Bet you can't hold your hand still.

Stage Direction

Show-Biz Science is scripted by popular children's book writer Vicki Cobb. Click to learn more about Vicki or to read a brief synopsis of her philosophy of teaching science.

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I’m a big proponent of informal learning -- creating a lesson out of a serendipitous moment. This lesson is something to pull out of your hat when you are sitting around a table waiting to eat. All you need is a metal paperclip in your pocket. A table knife is readily available. Kids also like a challenge: Bet them they can’t hold their hand still and they’ll be sure that they can beat the odds


Act I
Prepare for the action by unfolding a paper clip. Smooth out all the bumps and bend it into a "V" shape. Put the "V" upside down on the back edge (the smooth, or safe, edge) of a table knife's blade.

Act II
Have a student hold the knife over a table with the ends of the wire resting lightly on the table. The object is to hold the wire still. He or she may not rest the hand on the table or any other object. Amazingly the wire "walks" down the knife.

Be sure to try this experiment for yourself before having your students try it. You'll be amazed at how readily it works!

Behind the Scenes

The strangest part about this "walking wire" is that the harder a person tries to keep his or her hand still, the faster the wire walks down the knife. Muscles are made of cells that exist in alternating states of contraction and relaxation. When you contract your muscles to hold a position, only some muscle cells are in a state of contraction. Others are relaxing and recovering, getting ready to take their turn. That constant changeover creates a very slight motion or tremor that can't be seen easily. The walking wire magnifies this motion. The harder you try to hold your hand steady, the harder your muscles are working and the greater the difference between the tensed and relaxed parts of the muscle.

The End

The best athletes are relaxed during their efforts. That’s called being in “the zone.” A relaxed state makes the most efficient use of oxygen and fuel and gets the peak performance out of well-trained muscles.

Article By Vicki Cobb
Education World®
Copyright © 2005 Education World