Show I j r Physics in Fourth Grade SUBJECT SPECIFIC GI GRAVITY i jl Take Take a piece of lead or or r iron and anda nd a piece of cork hold them up in fullview full fullview view of the class and ask What these are are these objects I have in inn my in my y hand I c t. t e. e f fAns L Ans A piece of of- of f fI I lead d a and nd n d- d da a pie piece e of f cor cork k t tJ I t t I. I I I i j i jl i I r t Which is shea heavier r the Iea lead or orthe the cork rk Ans The l lead ld is heavier than the I. I I I. I cork Here is a larger piece of of f co cork I wh which ch chis is heavier it or the small pie piece e of lead The lead is h heavier vier I Which h is is r Ivo wood d or of or cork corkan an apple or a a ap piece p J of bf wood of of the same size an an n apple napple or ora a a piece orf of- f 20 cork cork k of of the j same same s size z f Y The correCt correct answers answers to these and liI like e questions will generally be given readily If they are not v ho however ver do not risk losing the attention n of f your pupils pupil's by trying too fob long to to bring out the answer answer to any any anyone one que question st n but fall bad back lu upon on something t easier a and d gradually l y lead from comparisons comparison which are very e easily si y made mad to more mf and more close d distinctions distinctions s in I. I 2 Take Take a vessel filled level with water place it in 10 full fullview view of th the ch children children chil chil- dren hold th the piece of I lead Idad a above If P and d as ask 1 I I r y tj I j. j I j Sj o. o J. J I It If T If-T I drop p the J l lea r th wafer JI w wafer t r j Jh J W what h a t WI will 11 1 it t d do O. O J S SW 1 r c It will wil gink 1 If If I I I- drop the cork cork in into o t. t the e water wate what what will it do Ans It will float In each case after the answer has been e n g given ven drop the object into the water and let all an see see whether or not the answer h has s been een correct Proceed in like manner with an apple a piece of wood a stone grains of Indian corn a apie apiece apiece pie piece e of chalk or any other materials easily obtainable verifying each answer 1 Call attention to the fact that the vessel I f is com completely filled with water place the vessel inside another preferably a abroad abroad broad flat d dish ish so that all the water which overflows will be caught and let leta letI I a child drop into nto the full ful vessel a rather large stone or piece of oi me metal al Now ask s' s v What has happened f d Ans The stone san sank k 1 v t. t 0 16 i And what else Ans Some water ran over 1 7 How much water ran over Ans As much as filled the place I now taken up by the bythe the stone t. t Next have another chi child Id drop into info the full v vessel an apple while all note effects It will be s seen en that tha t the apple does not go to the the bottom but still s some e water runs over Skillful questioning question question- ing will br bring rig out the fact that a volume volume volume vol vol- ume ume of water equal to the size of the part of the apple immersed is crowded out of the vessel Weigh the stone and the water it displaces the apple and the water it t displaces es Compare in each case the weight of the object with weight of water displaced 3 Weigh Weigh the piece of lead first in air then suspended by a string in water Note difference and proceed in inthe inthe inthe the same sarna way with iron apple chalk wood cork stone etc Be sure the children see that the difference between weight wei in air and weight in in water is equal in each case se to weight of water displaced This This will not be difficult I I unless the teacher herself e forgets and thus confuses es her pupils Now ask How many times heavier is lead lead- than water iron than water water the stone than water etc Is the chalk heavier or lighter th than n water the wood the appie apple apple ap ap- pie the cork With wh what t do you compare compare the weight of the lead the iron the apple the cork etc Ans With water Here introduce carefully the term specific gravity by means of f any device device device de de- vice which seems to you the most suitable suitable suit suit- a able le and use se it continually to denote the weight of a substance as compared with an equal volume of water If you find at a any y time that a child does not know the meaning of the term explain again objectively and keep on doing so until it is thoroughly understood l by byall byall all ll varying the ex examples mple used in order to avoid tiring the children with the monotony of the work 4 If 4 If the specific gravity of iron is i two and lead is twice as heavy as iron 1 what is the specific gravity of lead z Ans Four J If the specific gravity of iron is is two t and cork is one one fourth fourth as heavy as iron what is the specific gravity of cork A Ans s. s One This ex exercise cise may he extended through several recitations A good way is to combine the periods set apart for science science and number giving the whole time to this work for as many days a as the children children children chil chil- dren can b be kept in interested Teachers who have not tried thi this or a like plan will perhaps say that the work here outlined outlined outlined out out- lined is much too difficult for children of fourth grade but a fair trial will be sufficient to convince all such to the contrary I am satisfied that the most natural of all correlations is that between physics and number that any teacher who succeeds in making such correlation correlation correlation correla correla- tion will have solved many of the difficulties difficulties difficulties connected with the teaching of 1 both of these subjects to children and that such stich teaching ing in in the common schools will work a revolution in ln the methods of studying the natural sCle sciences ces' ces in schools of higher grade The work along this line in our training school has been so successful as to surprise even the most ardent ad advocates ate of correlation |