Because the lever enables the user to raise or move an object hundreds of times heavier than is possible without it, has led thousands of people to misunderstand its meaning, because it has the appearance, to the ignorant, of being able to manufacture power.
Wrong Inferences from Use of Lever.—This lack of knowledge of first principles, has bred and is now breeding, so-called perpetual motion inventors (?) all over the civilized world. It is surprising how many men, to say nothing of boys, actually believe that power can be made without the expenditure of something which equalizes it
The boy should not be led astray in this particular, and I shall try to make the matter plain by using the simple lever to illustrate the fact that whenever power is exerted some form of energy is expended.
In [Fig. 126] is a lever (A), resting on a fulcrum (B), the fulcrum being so placed that the lever is four times longer on one side than on the other. A weight (C) of 4 pounds is placed on the short end, and a 1-pound weight (D), called the power, on the short end. It will thus be seen that the lever is balanced by the two weights, or that the weight and the power are equal.
The Lever Principle.—Now, without stopping to inquire, the boy will say: "Certainly, I can understand that. As the lever is four times longer on one side of the fulcrum than on the other side, it requires only one-fourth of the weight to balance the four pounds. But suppose I push down the lever, at the point where the weight (D) is,[p. 130] then, for every pound I push down I can raise four pounds at C. In that case do I not produce four times the power?"
I answer, yes. But while I produce that power I am losing something which is equal to the power gained. What is that?