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Moments - The Lever Principle

The principle of moments can be used to move large objects with manageable forces. The Law behind 'The Lever Principle', famously summarised by Archimedes of Syracuse in the phrase, 'Give me a place to stand and I will move the Earth'. To apply the principle of moments, we choose a point to take moments about. A natural point to take moments about is a point about which turning might take place. In the diagram below this is the point O.

Taking moments about a point means working out the product of force and perpendicular distance for the anticlockwise forces:

And putting them equal to the product of force and perpendicular distance for the clockwise forces:obating the equation

Knowledge of any three ofwill mean we can work out the other one.

The Lever Principle is illustrated below. Taking moments about the balance point,

This means we can use a force of 653N to lift a weight of 1000*9.8=9800N.

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