Question

Why does a Tumbling Kelly toy return to its original position? (The oval shape is made out of plastic and lead at the bottom).

Answer 1

The toy has a state of stable equilibrium, in which the weighted lead has a tendency to stay at the bottom and overcome the moments that are produced in the upper parts. In other words, the oval structure allows the toy to oscillate and ensure that the weighted region is at the bottom, in its most stable position.