# Rotation with Zero Angular Momentum (The Square Cat)

Rotation with Zero Angular Momentum (The Square Cat)

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.