Question

a bullet hits a wall with a velocity of 20 m per second and penetrates it up to distance 5 cm. find the deacceleration of the bullet in the wall.

Answer 1

v = 0 
u = 20 m/s
s=5 cm = 0.05 m
Now, v² - u² = 2as
         0² - (20)² = 2×a×0.05
         0 - 400 = 0.1*a
         -400÷0.1  = a
          a = 4000 m/s²