Take the bottom of the chain and rasise it to the level, leaving the chain doubled and still hanging vertically.

The chain divided into small small sections each of length .

The chain doubled and still hanging vertically, the distance is .

The weight of the each section is the increment of force is .

Initially the chain is on the ground, and it is raised to height of , the increment of work is

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The length of the chain is 12 foot.

When it is doubled then the height became half.

The length of the chain ranges from to .

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