Physics Puzzle: Know Thy Center of Mass!

Posted on May 8, 2008
Filed Under Physics Puzzles |

Ok - this week you get two puzzles wrapped up in one. Here we go:

  1. You are given an arbitrary rigid object (say, a statue of the head of Elvis :) ) and asked to determine/estimate the position of its center of mass without doing any calculations. You can perform any simple experiment you’d like. Can you do it? Can you do it in under 30 seconds?
  2. You can balance a broom horizontally on your finger by placing its center of mass right on your finger. Suppose you’ve done that. Is the part of the broom to the right of your finger equal in weight to the part that’s on the left? If so, why? If not, give a counterexample.

As always - good luck & have fun!

Comments

One Response to “Physics Puzzle: Know Thy Center of Mass!”

  1. wandering.the.cosmos on May 29th, 2008 12:00 am

    1. Hang the rigid body by a thread 2 different ways; the intersection of the two lines extended from the thread is the center of mass.

    2. No. Just imagine a broom with a very thin and hence light shaft (i.e. of negligible weight), with one end tied to a heavy weight and the other end to a very light one. Then the center of mass would be much closer to the heavier mass, even though the longer side would be much lighter.

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