. A text book of elementary mechanics, for the use of colleges and schools. or, in general, W= 6P, W = nP, where n is the number of strings risingfrom the movable pulleys. This form of pulleys is the one whichis generally employed, though in practice,as remarked in Art. 226, the wheels areplaced side by side in two blocks. If in this arrangement theweight iv of the movable block istaken into account, the relation isthen W+iv = nP. 223. Third System. In the sys-tem of pulleys shown in Fig. 164,TT= (2* -1)P. The tension of the string onwhich the power acts, that is at a,is P; hence the pull on t
. A text book of elementary mechanics, for the use of colleges and schools. or, in general, W= 6P, W = nP, where n is the number of strings risingfrom the movable pulleys. This form of pulleys is the one whichis generally employed, though in practice,as remarked in Art. 226, the wheels areplaced side by side in two blocks. If in this arrangement theweight iv of the movable block istaken into account, the relation isthen W+iv = nP. 223. Third System. In the sys-tem of pulleys shown in Fig. 164,TT= (2* -1)P. The tension of the string onwhich the power acts, that is at a,is P; hence the pull on the wheelB is 2P, and this force is felt up-ward at b; still again, the pull on Cis 4P, or 22P, and. Fig. 164. PULLEY. 231 the same upward at e; also, on D it is 8P, and thesame upward at d. That is, the weight is supported bythe four forces; viz., P + 2P + 2aP + 23P = W = 15P = (24 - 1)P, or, in general, W = (2* - i)P. The tension on the beam is equal to TT + P, or 24P. 224. The following are other forms of pulleys, forwhich the relations of P to PFcan be established in thesame manner as for those already explained. In Fig. 165, W = 4P. In Fig. 166, W = 5P cos a(the tendency of the horizontal component of P is also tobe noted). In Fig. 167, W = 81P = 3*P.
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectmechanics, bookyear18