High School Physics

# Toppling, stability & the position of the centre of mass of a body

The position of the center of mass of a body affects whether or not it topples over easily. This is important in the design of such things as tall vehicles (which tend to overturn when rounding a corner), racing cars, reading lamps, and even drinking glasses.

A body topples when the vertical line through its center of mass falls outside its base, as in Figure 1(a).

Otherwise, it remains stable, as in Figure 1(b), where the body will not topple.

## Case studies to investigate Toppling

Toppling can be investigated by placing an empty can on a plank (with a rough surface to prevent slipping) which is slowly tilted. The angle of tilt is noted when the can falls over.

This is repeated with a mass of 1kg in the can. It will be found that the can with the mass in it can be tilted through the greater angle.

The same procedure is followed with a second can of the same height as the first but of greater width. It will be found that the second can with greater width & with the mass in it can be tilted through the greater angle.

## How to enhance the stability of a body

The stability of a body is increased by

1. lowering its center of mass, and
2. increasing the area of its base.

## Stand with one arm and the side of one foot together pressed against a wall and then try to raise the other leg sideways – can you do this

If we stand with one arm and the side of one foot together pressed against a wall and then try to raise the other leg sideways, then we will fall over.