29 
895 
A, = projection of A on To 
By = vrojection of B on TS: 
Let C, and T be defined as follows: 
(5.1) At Bat C= T 
(S22) gk MBO. 
T 18 a moving, broken surface, which is only initially coin- 
cident with T,. One would like to express the boundary con- 
ditions on ue in terms of boundary conditions on T, because only 
the latter are directly related to the coordinates of the sana 
Fortunately, the displacement of the block is emall. It is, 
therefore, assumed that 
(5.3) (Gano ae, 
Further, the flow behind the moving piston ia nearly one-dimension- 
al and incompressive. (In a shock of 300 atmospheres the density 
changes by about 1%.) If the flow 1a one-dimensional and incom- 
pressive tetween A, and A, then 22 = o there by the conservation 
of mass. Hence, 
(5.4) (4 3 (2 
by (5.1 = 4) 
| eae alan: 
oe (sz. = esl + (52), 24, 
or 
