Question

Explain how you will determine experimentally the position of the centre of gravity for a triangular lamina (or a triangular piece of cardboard).

Answer 1

Take a triangular lamina. Near the edge of triangular lamina make three fine holes at 'a ', 'b' and 'c'. Now along with a plumb line from hole 'a ' suspend the given lamina. Check that the lamina is free to oscillate about the point of suspension. Draw a straight-line ad along the plumb line when lamina has come to rest.​​

We get straight lines 'be' and 'cf ' respectively by repeating the experiment by suspending the lamina through-hole 'b' and then through hole 'c'.
It is noticed that the common point G is the position of the centre of gravity of triangular lamina where the lines 'ad ', 'be' and 'cf ' intersect each other i.e., the point of intersection of medians.