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Centre of gravity
Intermediate
The point where weight acts; equals centre of mass in uniform fields.
The point where the whole weight can be considered to act. In a uniform field it coincides with the centre of mass.
Balancing a ruler on a finger finds its centre.
On a huge body such as a mountain they differ slightly.
In more detail
The centre of gravity is the point where the total weight of a body appears to act. It coincides with the centre of mass when gravity is uniform across the body.
Real-world uses
- Tall structures are designed with a low centre of gravity to resist tipping.
- Gymnasts and divers control their centre of gravity during flips.
- A tall crane or a racing car is designed with its centre of gravity low, so it resists tipping over.
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Frequently asked questions
Is the centre of gravity always inside the body?
No. A boomerang or a hoop can have it outside the material.
Does centre of gravity change with orientation?
For a rigid body in a uniform field, the point is fixed relative to the body.
When are centre of gravity and centre of mass different?
Only in a non-uniform gravitational field, such as for a very tall object near a planet.
Related topics in Rotational Motion
Lever arm and moment · Equilibrium of a rigid body · Centre of mass of shapes · Stability and toppling · Moment of inertia · Moment of inertia of a rod