FOR 



horse employed to the same purpose. 

 The very best and most effectual posture 

 in a man is that of rowing, in which he 

 not only acts with more muscles at once, 

 for overcoming the resistance, than in any 

 other position ; but as he pulls backward, 

 the weight of his body assists by way of 

 lever. 



FORCE accelerative, or Retardive Force, 

 is that which respects the velocity of the 

 motion only, accelerating or retarding it; 

 and it is denoted by the quotient of the 

 motive force, divided by the mass or 

 weight of the body. So, if m denote the 

 motive force, and b the body or its weight, 

 and/ the accelerating or retarding force, 



then is/ as . Again, forces are either 



constant or variable. Constant forces are 

 such as remain and act continually the 

 same for some determinate time. Such, 

 for example, is the force of gravity, which 

 acts constantly the same upon a body 

 while it continues at the same distance 

 from the centre of the earth, or from the 

 centre of force, wherever that may be. 

 In the case of a constant force F, acting 

 upon a body 6, for any time t, we have 

 these following theorems; putting/ = 

 the constant accelerating force = F -r- 6; 

 s = the velocity at the end of the time t ; 

 V = the space passed over in that time, 

 by the constant action of that force on the 

 body: and^ = 16 J_ feet, the space ge- 

 nerated by gravity in 1 second, and calling 

 the accelerating force of gravity 1; then is 



= J to = sff = ~; * 



Zgt'gi* 4s-s 



FORCES variable, are such as are con- 

 tinually changing in their effect and in- 

 tensity ; such as the force of gravity at 

 different distances from the centre of the 

 earth, which decrea&es in proportion as 

 the square of the distance increases. In 

 variable forces, theorems similar to those 

 above may be exhibited, by using the 

 fluxions of quantities, and afterwards tak- 

 ingthe fluentsof the given fluxional equa- 

 tions And herein consists one of the 

 great excellencies of the Newtonian or 

 modern analysis, by which we are enabled 

 to manage and compute the effects of all 

 kinds of variable forces, whether accele- 

 rating or retarding. Thus, using the 

 same notation as above for constant 



FOR 



forces, viz. f, the accelerating- force at any 

 instant; t, the time a body has been in mo- 

 tion by the action of the variable force ; v t 

 the velocity generated in that time ; s, the 

 space run over in that time ; and = 16_L. 



e t A. ' VV ' ' 2 p- f s 



feet ; then is s = - == v t; v = * J 



= 2,/i i =i=^. ; /=^4. =^_ 



In these four theorems the force/ though 

 variable, is supposed to be constant for 

 the indefinitely small time t ; and they 

 are to be used in all cases of variable 

 forces, as the former ones in constant 

 forces ; viz. from the circumstances of 

 the problem-under consideration, deduce 

 a general expression for the value of the 

 force/ at any indefinite time t ; then sub- 

 stitute it in one of these theorems, which 

 shall be proper to the case in hand ; and 

 the equation thence resulting will deter- 

 mine the corresponding values of the 

 other quantities in the problem. It is 

 also to be observed, that the foregoing- 

 theorems equally hold good for the de- 

 struction of motion and velocity, by 

 means of retarding or resisting forces, as 

 for the generation of the same by means 

 of accelerating forces. 



FORCEPS, a pair of nippers, or pin- 

 cers, for laying hold of and pulling out 

 any thing forced into another body. 



FORCEPS, in surgery, &c. a pair of scis- 

 sars for cutting oft, or dividing, the fleshy 

 or membranous parts of the body, as oc- 

 casion requires. 



Forceps are commonly made of steel, 

 but those of silver are much neater. 



FORCER, or forcing- pump, in mecha- 

 nics, is a kind of pump in which there is 

 a forcer or piston without a valve. See 

 PUMP. 



FORCIBLE entry and detainer. Forci- 

 ble entry is a violent actual entry into a 

 house or land, &c.j or taking a distress of 

 any person, armed, whether he offer vi- 

 lenceorfearof hurt to any there, or furi- 

 ously drive any cut of the possession ; if 

 one enter another's house, without his 

 consent, although the doors be open, this 

 is a forcible entry, punishable by the law. 



And an indictment will lie at common 

 law for a forcible entry, though generally 

 brought on the several statutes against 

 forcible entry. The punishment for this 

 offence is by fine and imprisonment. 



FORCIBLE marriage, if any person shall 

 take away any woman having lands or 



