(3) Simple Machines and the Lever
116. Machines and Their Uses.—A man, while standing on the ground, can draw a flag to the top of a pole, by using a rope passing over a pulley.
A boy can unscrew a tightly fitting nut that he cannot move with his fingers, by using a wrench.
A woman can sew a long seam by using a sewing machine in much less time than by hand.
A girl can button her shoes much quicker and easier with a button-hook than with her fingers.
These illustrations show some of the reasons why machines are used. In fact it is almost impossible to do any kind of work efficiently without using one or more machines.
117. Advantages of Machines.—(a) Many machines make possible an increased speed as in a sewing machine or a bicycle.
(b) Other machines exert an increased force. A rope and a set of pulleys may enable a man to lift a heavy object such as a safe or a piano. By the use of a bar a man can more easily move a large rock. (See Fig. 83.)
