$\"\"$

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Force required to stretch a spring $\"\"$ inc on a exercise machine is $\"\"$ pounds.

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Therefore $\"\"$ N and $\"\"$ cm.

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Hooks law: $\"\"$ .

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Substitute $\"\"$ , $\"\"$ in the formula.

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$\"\"$

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$\"\"$

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Force required to stretch the spring $\"\"$ units is $\"\"$ .

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$ .

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

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Find work done in stretching the spring $\"\"$ foot from its natural position.

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Here $\"\"$ inches and $\"\"$ inches.

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Substitute $\"\"$ , $\"\"$ and $\"\"$ in integral formula of work done.

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$\"\"$

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$\"\"$ in-lb.

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$\"\"$ ft-lb.

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

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$\"\"$

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