The balance point of an object — Engineering, 7–10 years
An object is easier to balance when its weight is supported in the right place. Engineering, 7–10 years.
Find the balance point
Every object has a place where its weight seems to gather, called its centre of mass. If that place is above a support, the object can balance; if it falls to one side, the object tips. Engineers use this idea when they make things that must stand safely.
Why balance matters
A tall or uneven object may fall when a small push moves its weight beyond its support. That can damage a machine, spill a load or hurt someone. Engineers therefore ask where the weight is and make a wide base, add supports or place heavy parts low down.
A balancing ruler
Put a 30-centimetre ruler on one finger and slide it until it balances. Suppose it balances at 15 centimetres: the support is under the ruler’s centre of mass. Now clip a heavy peg at the 25-centimetre mark. The balance point moves towards the peg, so slide your finger right until the ruler is level again.
The middle is not always the balance point
It is tempting to balance every object at its geometric middle, because a regular ruler does balance there. But an object with a battery, a motor or a heavy lump on one side has more weight there. Its balance point moves towards the heavier part, even if the object’s shape has not changed.
Balance in real designs
A bicycle is easier to keep upright when its rider and frame keep the weight between the wheels. A toy excavator has a heavy base so its arm does not tip it forward. Engineers also check the balance of robots, cranes and boats before these machines carry or move anything.
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