Sun June 10, 2012 By: Kanu Singh

a bullet looses 1/20thof its velocity when passes through a wooden plank, find the least number of such planks to stop it? thank you

Expert Reply
Mon June 11, 2012
from 3rd eq of motion:
h=(39/400)u2 /2a
say if we keep n such planks,then the final velocity becomes 0after covering nh distance,ie the bullet stops.
nh=u2 /2a
n(39/400)u2 /2a =u2 /2a
n=10.2 ie 11 planks
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