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Show x" --~m‘\-u-x-.;r mu z,- 482 On tlae Vis Inertia qf Matter, 3 maxim that the force of bodies in motion is equal to the quantity of matter multiplied by the celerity, (OF/Zc‘xd); and as the force receiv- ed by and fubtil‘ting in matter, _when.it is put in motion, can never exceed the force given; 80 If: (M. P.] in a Letter to Mr. Baxter. 483 to move with 1 c (as they mig ht be by 2f] then the whole would mov e with 2 c, and not with r e as our author fuppol‘es. lint if applied to 2 ['2 makes each a more with e; and tie the whole. moves with I e; exactly the fame as 1 a was made to do by Ifbelore. What is equal cel erity but a flzeez/itrzhg tbejizme *‘/jfirzee by "moi/"23 ' 1mm z}: the 7" moves {2 with e, there mutt needs be required 2} to move a with 2 c; for a moving With 2 e would fame time ?-Now if 1 a impell ed by Ifmeafures have a force equal to 2f; which it could not re- if, each a mealiires 50 yards in a min ute, which added make 100; are not the celeriti es as the forces equal P and fince force and cele rity in the fame ceive from If; And this, not becaufe thereis inch 9. thing as Vis Inertiaz, for the cafe would be the fame flit/mt [7.4111720 exile/tee; but becaufe nothing can give more than it has-And now again, if a thing can give what it has, if rfcanto I ‘a glVC I c, which is the fame thing as givmg 1t ij; .(l.-C. if force applied to matter at ref't, can put-it in motion, and give it equal force ;) where then 18 V13 Inertia? If it exif'ted at all in matter, (hould we not find the quantity of its refiflance fubtraéted from the force given ? In No.4. our author goes on and lays, "the body " 4 requires a certain force to be imprefled on it to " be moved with a celerity as e, or fuch a force " is necelliiry; and therefore it makesa certain retittance, &c.: a body as 2 (1 requires Home that force to be moved with the jizme celerzty,' " or it makes twice that refil'tanee; and to on. ---ThisI think is not true; but that the body 2 (2 moved by the force 1f(thongh the eye mayJudge otherwife of it) does really move With the fame celerity as it did when impelled by the fame force; for 2 a is compounded of 1 a + l a : and ifeach of the I a's or each yart of the-compound were mail: 100 yards in aminute; andin 2 a imp elled. by quantity ofmatter are always in proper fzbfz to eac h other, Why {hould we, when the qua ntity ofmatter is doubled, allow the force to con tinue unimpaired, and yet fuppofe one half of the celei'ity to be loft*' P-I wonder the more at our author's * [Dr.Franklin's reafoning feems only to prove, that where bodies of differe nt maffes have equal force, they ‘ meafur e eylml {pace in ‘ equal times.' For allowing that 2 a moves 100 yards ina minute (becaufe it moves two {eparate 50 yards in that time) yet {urely that {pace is not the/hm: with that of the 100 yards moved by 1 a, in the fame time, though it may be equal to it: For the body 2 a (that is a and a) in the firlt cafe, delcribes a broad double (pace; and the body I a, in the fecond cafe, defcrib es a long and fingle {pace -There is a farther confideration which may (hear the difl‘u rence of celerity and force: For when Dr. Frankl in {ays in his fecond paragraph, that ‘ there is no mafs of matter, how great foever, " but may be moved, quit/1 an] rue/my, by any contin ued force, how ‘ {mall foever ;' [at]: whether the mowing lady mutt not have its force rather in the lhape of much celerity, than of much matter, for this purpofe; fince without much celerity it would not move talk enoug h to apply its force to give the required velocity ; even thoug h its quantity of matter, and confequently of force, were infinite.- ‘ Equal celerity therefore in moving bodies, is their meafuring equal ‘ fpace, along a marinara? line, in equal time.' Equal {pace meafurcd along a number offmaller parallel lines, fuits cafes of equal indeed, but, according to this corre€ted definition, not ofeguamtz'm / teleritJ. E.] _ (Lg q 2 mifiake ‘llllllllllllll‘l‘ll'lllfillll‘ w |