Central Stand Exhibits KL12 Rattleback


Does the sculpture defy the law of conservation of momentum?

Set the boat spinning anticlockwise and let it spin.
Next, set the boat spinning clockwise.

When you spin the boat anticlockwise, it spins for a long time until friction halts its spinning action. When you spin the boat clockwise, however, it begins to rock and, in the end, independently changes its rotational direction to anticlockwise.

Objects have three principal axes that are normally symmetrical in terms of rotation. This boat is not, however, as symmetrical as it appears. Its axes of rotation are angled in relation to its symmetry, and its weight is not evenly distributed. The rotational energy is divided from one oscillating frequency to another, and each axis has its own specific oscillating frequency. The spinning of the rattleback does not correspond to the characteristic frequency, and the friction slows the spinning. With each rocking motion, the boat sways a bit to the heavier side, and ultimately, the boat will turn to rotate in that direction.

Archaeologists discovered that the Celts used reverse rotation in some of their tools and weapons. The first attempts to explain the odd behaviour of the rattleback were made more than a century ago, but we still cannot adequately describe all aspects of its behaviour in terms of physical equations.

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