Sense of Equilibrium

The bird, that at first sight hangs in an unnatural way on its bill, the swinging parrot, the acrobat bear, the cyclist - are toys which show the question of barycentre. Hanging on a blade they don't fall, but swing lazily.

Balansujący ptak Balansujący ptak

In all these toys the natural barycentre has been moved by adding some weight in a way to make the real barycentre lay exactly under the point of support. If we put them in an oscillatory motion they swing slowly because the barycentre is not far from the rotation point, while the moment of inertia is big.

Where is your barycentre when you are in equilibrium over a rope? Do we need to bring some heavy luggage in order not to fall down?

Butelka

Reaching the state of permanent equilibrium requires taking some measures aimed at moving the centre of gravity away from its 'original' place.


In the case of the bird adding extra weight to its wings moves the centre of gravity towards its beak, so that when it is balancing the centre of gravity is just below the fulcrum. Similarly as in the case of teddy bear the rope walker holding a curved stick with weights (spheres). The parrot and toucan are also swinging safely on the support rod after adding extra weight to their tails.

In contrast to the parrot which is flat, the bird can serve illustration of yet another aspect of centre of gravity location. Its 'proper' positioning is two- (or rather three-) dimensional. Viewed from above, the wide spread wings of the bird and its tail are in the shape of a triangle with the centre of gravity in the fulcrum. Viewed from the side, the lowered tips of the wings make it possible to move the centre of gravity below the fulcrum.


When we set the toys in the oscillatory motion they move lazily, like the swinging head of the dog.

The simplicity of such kind of toys enables experimenting with the various centre of gravity locations, as for example in 'moon jigsaw', or 'kitchen' bird model.

Księżyc Rower na linie
Zabawka
Widok Zabawka z moneta