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RE: Newton's 3rd Law



Hi Tom Koch-
I don't understand your demonstration of Newton's 3'd law. You
write:
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I have had some success introducing Newton's Third Law by letting students
play a game for a few minutes. It's based on a game with murky origins which
my family plays at holiday get togethers, and demonstrates Newton's Third Law
and Center of Gravity / Toppling in a kinesthetic way. (I try to get
students to picture my family playing the game, which they find humorous.)

Pair students up, and have them face each other, standing an arm's length
apart, with feet at about shoulder width and hands (fingers pointing up) at
about shoulder height. The object is to get the other person to move his/her
feet (to avoid falling). The rules are that you can only hit (or avoid) the
other person's hands (no grabbing), and you may not move your feet. The
trick (and the connection to Newton's Third Law) is to decide when to provide
a reaction force for the other person's push and when not to provide a
reaction force.
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But there IS a reaction force whenever there is contact, whether
or not the other person decides to provide resistance.
Regards,
Jack