$\"\"$

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Force required to hold a spring stretched $\"\"$ in beyond its natural length is $\"\"$ lb.

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Hookes law : $\"\"$ , where $\"\"$ spring constant.

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$\"\"$ is force required to maintain a spring stretched $\"\"$ units beyond its natural length.

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Here $\"\"$ lb and $\"\"$ feet.

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$\"\"$

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Therefore, spring constant $\"\"$ lb/ft.

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Determine the work done in stretching the spring from its original length to $\"\"$ in $\"\"$ feet.

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Consider $\"\"$ .

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Work done formula:

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Work done in moving the object from $\"\"$ to $\"\"$ is $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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Work done is $\"\"$ ft-lb.

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$\"\"$

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Work done is $\"\"$ ft-lb.