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Torsion Balance

Precise measurement of mass is an essential task in scientific inquiry. Most weighing machines are called "balances" because they employ a beam balanced delicately on a central sharp edge (called the fulcrum). Unknown weight applied to one side pulls the beam off-center. The weight of the sample can be found by adding standardized weights to the other side until the beam is balanced. This torsion balance is novel in that it does not use a beam resting on a central fulcrum, rather the beam is suspended by taut metal bands. The weight of the unknown sample places a subtle twisting, torsional, force on the bands. Again, by adding known weight to the opposite side, the torsion is balanced, and the value of the unknown is determined. Nutritionists in the NIH Clinical Center used this particular instrument for many years to formulate special diets for patients.

Torsion Balance
Torsion Balance

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