A solid, strengthless copper penetrator of length $200$ mm impacts a target that comprises $20-mm$

tungsten $(W),10-mm$ polycarbonate $(PC)$ and $10-mm$ copper $(Cu).$ The projectile is travelling at $5$

$k\frac{m}{s}.$ Assuming that one$-$dimensional penetration and all materials are strengthless, calculate the

velocity of the penetrator in each layer assuming that each plate behaves like a semi$-$infinite plate.

What is the length of the rod that exits the target?

The densities of materials are as follows:

W: $19,250k\frac{g}{m^3}$

PC: $1210k\frac{g}{m^3}$

$Cu$:$8960k\frac{g}{m^3}$