1That's cool, thx.
A bullet loses 1/20 th of its velocity on passing through a plank. Assuming the planks exert a constant retarding force, what is the no. of such planks required to just stop the bullet?
Options given, but I'd rather someone solve it without them.
If it's the answer, then post the method.
If it's a formula, then post the derivation.
Please.
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UP 0 DOWN 0 0 2
2 Answers
21v2=u2-2as...........a is retardation
initial velo u
final velo wen the bullet passes through first plank is 19u20
s be length of one plank
2as=u2 -(19u20)2 ................i
let n be the planks after which through passing the velo of the bullet becomes 0
total distance=ns
final velo 0
so.... 2a(ns)=u2.......ii
dividing eq i and ii we get n=400/39 ≈11