$\"\"$

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The masses are $\"\"$ .

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The coordinates are $\"\"$ .

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The moment of the $\"\"$ - axis is $\"\"$ :

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$\"\"$

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$\"\"$

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$\"\"$ .

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The moment of the $\"\"$ - axis is $\"\"$ :

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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The sum of the masses is $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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The center of the mass is $\"\"$ .

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

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$\"\"$

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$\"\"$ .

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$\"\"$

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The center of mass is $\"\"$ .