Centre of gravity of lamina

The centre of gravity of a lamina is simply the point where the entire weight of a flat shape appears to be concentrated. For simple geometric shapes like rectangles, triangles, and circles, finding this point becomes straightforward because these shapes have predictable balance points.

For a rectangular lamina like a wooden signboard commonly seen in Nigerian markets, the centre of gravity sits exactly at the intersection of its diagonals—right in the middle. For a triangular lamina, it's located at the point where all three medians meet, which is about one-third of the height from the base. A circular lamina balances perfectly at its centre point.

Understanding these positions matters because it helps you predict how objects will balance and rotate. When you're drawing these shapes in your technical drawing exam, always mark the centre of gravity clearly with a small cross or dot.