or△ △P (193) B 3How to find the displacement of an element of gas inside the tube? The undisturbed density of Oxis OX ox A is the corss- iS(x+Sxt) Aδx sectional area SIX 8x=x"x′=[x+x+(x+8,)-x+8x+(x: xx 6x[1+ S(+ar, t-s(x 6x[1+ Sm ASx 1+osar P(1-as/Ox), if as/ax <<1 △p=p-po=-pOs/Ox (196)3) How to find the displacement of an element of gas inside the tube? B m Pm  0  =  (19-3) x=0 x s(x,t) s(x+ ,t x ) x' x x’ x’’ x A x m   0 = The undisturbed density of is x A is the corss￾sectional area. x ' = x ''-x' = [x + x + s(x + x ,t)]−[x + x + s(x ,t)] ] ( , ) ( , ) δ [1 x s x x t s x t x  + − = + (1 ), 1. ' 1 0 0       +   = = ρ - s/ x if s/ x s/ x ρ A x δm ρ  s x  = −0 = −0  /  (19-6) or ] s δ [1 x x   = +