Find the centre of mass of a triangular lamina.

Explanation

The lamina `(DeltaLMN)` may be subdivided into narrow strips each parallel to the base (MN) as shown in fig.

By symmetry each strip has its centre of mass at its midpoint. If we joint the midpoint of all the strips we get the median LP. The centre of mass of the triangle as a whole therefore, has to lie on the median LP. Similarly, we can argue that it lies on the median MQ and NR. This means the centre of mass lies on the point of concurrent of the medians, i.e. on the centroid G of the triangle.