$\"\"$

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Work done required to stretch the spring $\"\"$ ft beyond its natural length is $\"\"$ ft-lb.

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

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Here $\"\"$ , $\"\"$ and $\"\"$ .

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From the Hookes law , $\"\"$ .

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Substitute $\"\"$ , $\"\"$ , $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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

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Determine the work done in stretch the spring $\"\"$ in beyond its original length.

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Consider $\"\"$ .

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Here $\"\"$ and $\"\"$ in $\"\"$ foot.

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Work done is $\"\"$ .

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$\"\"$

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$\"\"$ ft-lb.

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

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$\"\"$

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