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A great demonstration for rotational inertia

  • Both wands have the same mass but different rotational inertias
  • The red wand is much easier to rotate
  • Challenge students to explain why

Rotational Inertia Wands

ME-9847

$7500

U.S. Educator Pricing

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Description

These two wands have the same mass and the same dimensions and yet the red wand is easier to rotate.  Why?  Because the red wand has two metal slugs near its center while the blue wand has two similar slugs at its ends.  This demonstrates that rotational inertia depends not only on the mass, but how that mass is distributed relative to the axis of rotation.

These sturdy plastic wands have small holes near the center and at the ends to enable students to see where the metal is located in each wand.  So what initially seems a mystery can be discovered and explained by the students by allowing them to examine the wands more closely.

To demonstrate the difference in rotational interia of the two rods, ask two students to grab the center of a wand and rotate it back and forth as rapidly as they can. No matter how strong the student with the blue wand is, he or she will not be able to rotate it as fast as the student with the red wand.

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