Weebles wobble but they don't fall. I came to know that they wobble and come back to position since the center of mass lies close to the bottom. Can I apply the formula for center of mass and do a human weeble as in In that case if I consider a hemisphere of radius 60 cm and the average weight of a person as 70 Kg (M2) and height of the person as 175 cm. The center of mass of the person is at his middle at 87.5 cm (R2) from the top of the hemisphere. My aim is to find the mass (M1) to put at the bottom for it to act as a weeble. The center of mass of the system must be at the bottom say 30 cm (R1) from the ground into the hemisphere. By considering a coordinate system with COM at (0,0), M1 at R1 (- 30,0) and M2 at (117.5,0) M1 =( M2* R2) / R1 M1 = 70 * 117.5/ 30 = 274.2 kg But this seems very large! Is it right? Will I be able to build one?