If a body looses half of its velocity on penetrating 3 cm in a wooden block, then how much will it penetrate more before coming  to rest

For first conditionInitial velocity = u, Final velocity = u/2, s = 3 cmFrom v2=u2−2as⇒u22=u2−2as⇒a=3u28sSecond condition Initial velocity = u/2, Final velocity = 0 From v2=u2−2ax⇒0=u24−2ax∴x=u24×2a=u2×8s4×2×3u2=s/3=1 cm