| Show What the Physicist means ly Work and Energy Suppose a gardener with a ton of gravel in front of him were told to movs that gravel to ft height of three feet He would go to work with his spade he would move shovelful after shovelful from the ground line up to threefeet height and after hehad moved the whole of it you might readily imagine that he would belittle s be-little fatigued Now whenever a peraon does anything which causes fatigue he does what we call work The gardenar in lifting the gravel would perform an amount of work which is capable of being measured I will give you another illustration Supposing some of you boys were put beside a pile of cricket balls and for a wager or prize you are called upon to throw the bails as fast and as far as you could A good thrower would psrrhps throw the first ball eighty yards he would throwthe second ball seventyfive yards 1 the third seventy the fourth sixtyfive yards and so each ball that he thew would go a leas and less distance until be had no strength left and he would throw no more balls Now that boy would have done work something would have passed out of him into the ball he has as it were passed something that belonged Lto him into the cricketballs and as a result be fetid l fatigued through the loaa of this something Take another illustration = illustra-tion Supposing two crewa agree to row a race They start full of life and full of energy they pull with I all their hearts and might and arrive at the goal in common language I thoroughly pumped out Something has gone out of them into the boat That which baa gone out of the crew and out of the boy who threw the cricketballs is what we call energy and what they have done is to do work upon the boat Another example ex-ample is in the case of football A boy kickR a football and makes a I splendid goal To do that he has sent something out of his body into the ball which hurtles through the air pa3t the goal and the game is won In all these illustrations something is done which results in fatigue work is performed and energy ia lost in fact work done weans energy applied ap-plied and energy applied means work done As mental energy ia our capacity for learning leaaonr for gciiJE through examinations and that kind of thing eo the energy of the kind I speak of is the capacity for doing absolute physical work The generality gener-ality of this energy is immense It is a difficult thing to grasp the fact that there is something in existence that we cannot feel that we cannot touch and that we cannot see but which gives us all the force and all the power we PO8tS3Popularl Science Monthly |
