Centre of Mass and Moments
Centre of Mass and Moments
- The centre of mass of an object is the single point that you can consider its whole weight to act through (whatever its orientation).
- The object will always balance around this point, although in some cases the centre of mass falls outside the object.
- For a uniform regular solid, the centre of mass is at the centre of the object.
Finding the centre of mass by experiment
You can find the centre of mass of a flat object using a simple experiment:
- Hang the object freely from a point (e.g. one corner).
- Draw a vertical line downwards from the point of suspension — use a plumb bob to get your line exactly vertical.
- Hang the object from a different point, and draw another vertical line.
- The centre of mass is where the two lines cross.
Forces of supports
- If an object is being held up by supports (e.g. chair legs, car tyres, etc.), the force acting on each support won't always be the same. The closer the object's centre of mass is to a support, the stronger the force on the support. It's all to do with the principle of moments — the anticlockwise and clockwise moments must be equal. So a support closer to the centre of mass will experience a larger force.
Questions
- \(24000 \times 9.81=235440\) | \(235440 \times 3.5=824040\)
- The centre of mass of an object is the point where the mass is concentrated.
- The centre of mass of a uniform object is the centre of the object.