WOLFRAM|DEMONSTRATIONS PROJECT

Rotation with Zero Angular Momentum (The Square Cat)

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arm length
base angle
A deformable body can rotate itself using only internal forces—without any external torque, keeping its angular momentum zero. This is the case for a cat falling from a tree and landing on its feet. The four masses at the vertices of a parallelogram in this Demonstration can also rotate with only internal forces changing the parallelogram's base angle and arm length.