Writing 



V £ = V + u£ m) + u f (52) 



Equation (28) can be written 



111 / m \ TT 



V 2 V \ V V 7 2 V V 



s s \ / s 



v~ ( 2+ ~ s ~ ) = ~ V~ s I 1+ H " -v" + ° V- (53) 



G U T U f m 



if rr^- is as small as — or ■=— , terms including G u and G u can be neglected, 



s 



80 



