Center of mass

The center of mass of an object is a very particular point that physicists use to study the motion of an object or its equilibrium.

Every object has a center of mass. If the shape of the object is weird, or if it is heterogeneous (made up of materials of different densities), then this point can be difficult to find, but it still exists.

It is very interesting to locate it, because it will then be possible to study the motion or equilibrium of the object by applying the laws of physics to this single point rather than the whole object.

This animation allows you to draw two-dimensional shapes with the mouse or finger. The object made is supposed to be homogeneous (made of a single material). The center of mass is calculated automatically. Note that if the shape is symmetrical, the center of mass is on the axis of symmetry. If the shape is a circle, the center of mass is the center of the circle. If the shape is not symmetrical, the center of mass is shifted to the side where there is the most matter (more mass). It is possible for hollow shapes, or concave shapes (such as a boomerang) that the center of mass is outside the object.

The center of mass as a point becomes very interesting if we study the balance of an object:

• If the object hangs motionless at the end of a wire, then the center of mass is aligned with the wire.
• The only way to make the object balance above the tip of your finger is to place your finger very precisely just below the center of mass.
• If the object rests motionless on a table, we can assume that its center of mass is somewhere above the segment that joins the points of contact (also called a "Base Area"). If the center of mass is outside this segment, the object is no longer in equilibrium, and it would tilts.

Gymnasts and dancers excel in this mastery of balance. The same goes for the Inuit sculptures of Baffin Island artists.

Thanks:

• Galerie Art Inuit Brousseau, Quebec
• Artists from Kinngait, Nunavut: Pudlalik Shaa, Adamie Quamagiak, Padlaya Qiatsuq.