g^ ON THE MOTION OP ROC-iETS. 



■ ^ets, - V ' "" ~r^) ~ "^'""^^ "' *^'^ present 



^(jn of rcckets, 



case is equal to the sine of the an^yle P T W or P W R, 

 Now because of the oblique action of the fluid against the 

 cylinder, (considering the fluid in motion, and the solid at 

 rest) its force on this account will be diminished in the ra- 

 tio of radius to the cube pf the sine oi the angle of incidence, 

 or as 1 to/^ Therefore considering T P the representative 



— Z — J » 



its efficacy to move the cylinder in direction P T 



villbePRand - "-^lI . gin' / PWR = 



4g 



Hj ' —r^ = Agr^ • <^' -/* ^*>- '^^^^^^^'•^ 

 the fluxion of the force of tiie fluid on F T will be 



- /I ^ 



- — li- iV* _^ ri r*\ —_: ^' — 7 ^ > 



Hr-'' ^^'- ^S77'' ^ 



or 

 nv'-p A {T-^ — f^ x'-y' 



Asr 1 



the fluent of which is \ 



(r + 5). (r — ^? , 



' j,p „1 " -i +• &c.)- which when x zz r 



is ^i^' (1 _ tZlzLi . s{,/;^i)'- 



4g- ' 6 ^ 40 ^ 



rr^; + &c.) . This therefore is the 



effective force of the fluid on the quadrantal arch F T S. 

 Hence the force on the whole semicylindric surfaces DrrBs 

 _ nv^ thp /■ 3r — l 3{/«— 1)2 



2g V' 6 + —45 + 



:^- + &c. J which is also the re- 

 sistance to the cylinder when this moves in the fluid at rest, 

 »s far H8 relates to that surface. Q. E. I. 



Yours, &c. 



W. MOORE. 



