Moment of Inertia Demonstration
| The two rods are of equal mass.
For one of the rods the mass is concentrated mainly in the center.
For the other, the same amount of mass (placed in the center of the
first) is divided equally between the two ends. If they are rotated about an axis perpendicular to the rod and running through the center, it is more difficult to rotate one than the other. Why? If they are rotated about an axis on one of the ends and perpendicular to the rod, there does not appear to be any difference. Why? The moment of inertia is a measure of an object's resistance to changes in rate of rotation. It is the rotational analog of mass in linear motion. Since I is given by mr2, the rod with the mass near the center has a lower I if rotated about the center. If they are rotated about an end, however, the moments of inertia should be about the same. |
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