The thrust obtainable from a propeller depends on three variable quantities :
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(1) The revolutions per second (n).
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(2) The dimensions of the propeller.
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(3) The slip (s).
Two further quantities are involved, the Torque (M) and the Power (H), but these are both dependent on the three preceding.
Assuming, in the first place, a constant slip (say, 100 per cent.), and choosing any convenient vaiue for the revolutions, we immediately fix a relation between the power consumed and the torque.