All About Engines

20 All About Engines 7 lb., we can calculate the work done in the following way •: Distance moved by force in one revolution1 . . . .=2x^x1 = ft. Work done in one revolution = x 7 = 44 ft.-lb. And for 20 revolutions, 44 x 20 = 880 ft.-lb. would be required. It will be evident that work can be stored up in a body which is lifted or deformed, or set in motion. A weight of 14 lb. raised to a height of 5 ft. will have had 70 ft.-lb. of work done upon it, and there will be 70 ft.-lb. of energy, or ability to do work, stored up in it. For in falling back to its former position it can be made to draw a rope or a pulley, or raise by means of a lever another weight. But it would not do 70 ft.-lb. of work because the lever or pulley would produce friction, and work would have to be done to overcome that. Similarly the gas would not push the piston back quite to its original posi- tion because of the friction against the walls of the tube. And finally the grindstone or mangle would turn for a time after the force was removed, and would in this way raise a weight. Compare also the action of the flywheel described on p. 8. But even these will not give back all the work that has been put into them. 1 The circumference of a circle is 3 J or 2T2 times the diameter. Hence the circumference of the circle formed by the handle of the grindstone is 2 x y =