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The Common Balance

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-102

2025-11-06

708

is a lever of the first class with equal arms, hence in this case P = W. In order that the balance may be accurate, the arms, or parts of the beam on each side of the fulcrum, must be of equal weights and lengths. In order that it may be sensitive, the arms must be light, the friction must be little, and the knife-edge fulcrum must be very close to a line joining the knife-edges of the scale pans, with the center of gravity of the arms just below it.

Even if a balance does not fulfill the conditions for accuracy, the true weight of a body may be found with it by the method of substitution as follows: First counterbalance the body exactly by putting sand or any other convenient substance in the other scale pan. Then remove the body and substitute for it known weights until they exactly counterbalance the sand. The sum of the weights required will be the weight of the body.