First case
initial velocity(u)=v , final velocity(v)=v/2 ;distance covered(s)=3cm
we know 2as=v2-u2
2*a*3=(v/2)2 - v2
a= -v2 / 8
in second case
initial velocity(u)=v , final velocity(v)=o ;distance covered(s)=we hav to find out
here we know acceleration=-v2 / 8
2as=v2-u2
2*(v2 / 8)*s=(0)2 - v2
on solving we get
s=4cm
but it had already pnetrated 3 cm thrfore it will pertrate 1 cm more to come to rest
