Centre of Gravity vs. Centroid: Key Differences Explained
Centre of Gravity is the single point where an object’s entire weight acts. Centroid is the geometric center of a shape, found by averaging all its points. They only coincide when the material is uniform and gravity is uniform.
Engineers sketch a beam and label “CG,” students label “Centroid,” and both arrows land on the same dot—so everyone assumes the words are synonyms. In real life, a hollow pipe and a solid rod can share a centroid but have different centers of gravity, creating the confusion.
Key Differences
Centre of Gravity depends on mass distribution and gravity; Centroid depends only on geometry. For a seesaw made of mixed materials, the Centroid stays centered, but the Centre of Gravity shifts toward the heavier child.
Which One Should You Choose?
Use Centre of Gravity when balancing or lifting objects, like rigging a crane load. Use Centroid when calculating beam deflection or designing logos, where weight and gravity don’t matter.
Examples and Daily Life
Imagine a smartphone: the Centroid is its exact middle, guiding case design. The Centre of Gravity sits closer to the battery, so it feels heavier on one side when you hold it.
Can a shape have a Centroid but no Centre of Gravity?
No. Any physical object has mass, so both points exist; only the locations may differ.
Do architects care about both terms?
Yes. They use Centroid for symmetry drawings and Centre of Gravity for structural safety checks.