Mechanics · Moments
Chapter 1 · 3
The idea
Centres of mass of laminas, frameworks and particles
How to find the single point where a body's whole weight acts, for particles, uniform laminas (composite, cut-out and folded) and wire frameworks, and how to use it to find the angle a freely suspended body hangs at, or the particle or force that holds it level.
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Mechanics · Moments
Centres of mass of laminas, frameworks and particles
How to find the single point where a body's whole weight acts, for particles, uniform laminas (composite, cut-out and folded) and wire frameworks, and how to use it to find the angle a freely suspended body hangs at, or the particle or force that holds it level.
Why it works
The one point that decides how it hangs
A sign-maker cuts an arrow from a uniform sheet of metal and hangs it from a single hook at the corner . It does not hang level. It swings, then settles tilted, like this. Why that angle, and not another?Every scrap of the sheet is pulled down by gravity, but those pulls add up to one weight acting at a single point, the centre of mass . While is off to one side of the hook, the weight has a moment about and the sign keeps turning. It stops only when that moment is zero: with directly below the hook. So this whole topic is two jobs. Find . Then use it.Keep reading — free
The rest of the explanation, plus 4 worked examples you step through move by move.
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