-23- 269 



33 ft. above sea level, we have 



(2.30) ^opt. "^ '^'^^ ^r~ atmospheres 



where W is the weight of T. N. T. in pounds and R is 

 the distance from the center of the bubble In feet. 



This may be compared with the peak pressure of the 

 primary shock wave, whose value, experimentally obtained, is' 



P , . = 1160 — « — - atmospheres. 



The optimum peak pressure of the secondary pulse is approxi- 

 mately 15 percent of the shock wave peak pressure, but the 

 duration is much longer, as will be seen in the next section. 



9. The impulse . 



The impulse I per unit area, carried by the secondary 

 pulse, is the time integral of the pressure. 



I = / PdT = C / Pdt, 



where the limits of integration are the times when ? = ot 

 By (2.26), 



2* • 

 where the limits of integration are the times when (a a) = 0. 



Using the fact that the motion is approximately symmetric about 



* See [3] page 13, where this experimental result is quoted 

 in metric units. 



Hi- The significance of this value of the Impulse will be 

 discussed later. 



