Physics – 1.5.3 Centre of gravity | e-Consult

The stability of a simple object is directly related to the position of its centre of gravity (CG) relative to its base of support. A lower centre of gravity generally leads to greater stability. This is because a lower CG means a larger torque (rotational force) is required to tip the object over.

Consider a rigid plank. If the plank is supported closer to its centre of gravity, it will be more stable. If the support is moved further away from the CG, the plank becomes less stable and is more likely to tip. Similarly, a stack of blocks is more stable if the heavier blocks are placed lower down, bringing the CG closer to the base. A higher CG in a stack of blocks makes it more prone to toppling.

The base of support is the area over which the object rests. A wider base of support also contributes to stability, but a lower CG is a more fundamental factor. The relationship is essentially a matter of torque: the greater the torque required to overturn the object, the more stable it is.