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cident wave travels slowly after passing through the head 
of the reflected wave on its way to the wall. Consequently 
the reflection is prolonged and the impulse is increased. 
il. The momentum in the reflected pulse is easily 
found from such pressure-time curves as are shown in fig. 
2 - 4. The equation of momentum transfer for one-dimensional 
flow is (fig. 6) 
where the subscripts refer 
watt oe to two planes perpendicular 
to the motion and separated 
by the distance Xo ~ Xz 
P Pu, P Patt, Delt. and » are pressure, 
velocity, and density. Choose 
the plane x, at the rigid 
wall and the plane xp in un- 
x, a Xz disturbed fluid. Then 
Fig. 6 (11.1) becomes 
- 9.) 2 
Py St x] f u dx, 
and after integration one has 
t Xo t 
\ p, dt = J f vax (11.2 
fo) xy G 
