Chapter 11

This is one of my favorite chapters. I appreciate this chapter very much because it demonstrates a world of mechanics which is a field that I am likely to study in. to begin with this chapter the book quotes a remarkable ancient saying which is “give me a fulcrum on which to rest, and I will move the earth.” --- Archimedes, 2nd century B.C. I knew this quote when I was in elementary school, and I was intrigued by the mysteries of mechanics at that time.

Not only the modern technologies but also the ancient civilizations depend greatly on the use of machinery. Without the help of mechanical tools, the giant pyramid would not be completed, nor would the great wall and the Stonehenge. Machinery such as lever, pulley, wheel and axle, intermeshing gears, inclined plane, wedge, and screw provide extremely effective and energy saving assistance to people because these basic machines serve three purposes which are increasing speed, increasing force, and change the direction of a force. Intricate machinery combines these simple machines and serves two or three of the functions simultaneously. One outstanding superiority of machinery is the reduction of the amount of force put into the work; however, a saving of force in a machine is at the expense of long distance because according to the law of kinetics, disregarding the losses due to friction, the work put into a machine equals the work put out and there is a formula that work is the result of the multiplication of distance and force; therefore, when the force is reduced, there must be an increase of distance if the total amount of work is identical.

The law we refer here is just theoretical; in fact, all machines lose some of their efficiency because of friction in reality, and friction occurs when any two substances rub together. Some frictions are totally awful, for they waste energy; in addition, the heat that results from these frictions cause severe damages to machines. In order to reduce the harmful frictions, people fill lubrication into the irregularities of the contacting surfaces of the parts in machines. On the other hand, frictions can also be an asset in consideration of they preventing slipping and making possible thousands of every day activities.