# Do Some Physics Before Shooting!

Jim, the scientist, is planning to do a dangerous stunt in which he puts his life at stake. He asks his assistant to shoot him while he stands behind a stack of identical books.

Before he does the stunt, he test fires a bullet on a single book and confirms that the bullet fired at speed $$\SI[per-mode=symbol]{457.2}{\meter\per\second}$$ penetrates the $$\SI[per-mode=symbol]{3.5}{\centi\meter}$$ thick book and comes out from the other side at speed $$\SI[per-mode=symbol]{400}{\meter\per\second}$$.

What is the minimum number of books Jim needs to stack up so that he can pull off this stunt safely?


Details and Assumptions:

• Air resistance is neglected.
• The deceleration of the bullet within the books is constant.
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