[Illustration: FIG. 103.--Primitive man tried to lighten his task by
balancing his burden.]
Prop the board so that the end _A_ is 2 feet above the table level;
that is, arrange the inclined plane in such a way that its length is
twice as great as its height. In that case the steady pull on the
balance will be one half the weight of the roller; or a force of 6
pounds will suffice to raise the 12-pound roller.
[Illustration: FIG. 104.--Less force is required to raise the roller
along the incline than to raise it to _A_ directly.]
|