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Stability and toppling
Intermediate
A body topples when the weight line falls outside its base.
A body is stable if the vertical line from its centre of gravity falls within its base. Lower centre and wider base are more stable.
A bus tilts safely until the weight line passes the wheel edge.
Tall, narrow objects topple easily.
In more detail
A body tips over if the line of action of its weight passes outside its base of support. The wider the base and the lower the centre of gravity, the more stable it is.
Real-world uses
- Racing cars have low centres of gravity for stability in corners.
- Furniture is designed with wide bases so it does not topple.
- A tall cupboard or a fully loaded lorry tips over when its weight line moves past the edge of its base.
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Frequently asked questions
Why does a wide base help?
It keeps the line of action of the weight within the support area for larger tilts.
Does height matter?
Yes. A higher centre of gravity makes tipping easier.
How can I make an object more stable?
Lower its centre of gravity and widen its base, so the weight line stays well inside the support.
Related topics in Rotational Motion
Equilibrium of a rigid body · Centre of mass of shapes · Centre of gravity · Moment of inertia · Moment of inertia of a rod · Moment of inertia of a ring