TNVESTICATKI) BY TFIK METHOD OF JKT VIBRATION. 359 



If the jet is parallel to the plane through the edges, but makes an angle of 90 < 

 with these, then the total length of the portions cut oft' during a complete swing 

 will l>ecome 



If the jet is at right angles to the edges, but makes the angle to with the plane 

 through the edges (see fig. 7), the conditions are a little more complicated. In 

 the figure the jet is drawn in two positions, S, and Sj. The one position, S,, gives a 

 picture of what takes place with the "jet-catcher" moving in one direction, S, gives 

 u corresponding picture of the movement in the opposite direction. V is the velocity 

 of the jet. With regard to the other symbols, reference is made to the figure. 



We have 



I/, = L, sec a +1/1, t/, = V/t'i . .r,, or, = LI tan &>, 

 also 



L', = L^sec oi + V/u,. tan o>) ........ (3). 



In the same manner we get 



L', = L,(seca>-V/r s .tana) ........ (4). 



By the addition of (3) and (4) we get 



L = L', + L',= (L I + L,)[8ecw + Vtan<o(l/r 1 -l/r !l )] . . . . (5); 



as the last term is so small that we can take L, = L, without any appreciable 

 error. 



If v, = tfe 



L = (L, + Lj,).seca> . ' ........ (6). 



In practice v l and v t will have almost the same value, although the velocity will 

 naturally be somewhat smaller each time the "jet-catcher" passes the jet. To 

 investigate the influence of this difference in velocity we take v 3 = 0'9t',, V = r,. 



The equation (5) then becomes 



L = (L l + L s ).(sec&>-0 > 0555tana>) ....... (7). 



By t>, = 0'9r, and V = t' a , equation (5) becomes 



L = (L, + Lg). (sec 01 + 0-0555 tan co) ....... (8). 



To judge the influence of the angle o the Table I. is available, which also contains 

 the corresponding values for r s = 0'95r, and r, = 0'95v^ 



In practice the ratio between v, and v a will still more approach to 1. As can be 

 seen, no especially great exactness is required in the adjustment of the "jet-catcher" 

 relatively to the jet. 



