A bullet moving with a velocity of 200 cm/s penetrates a wooden block and comes to rest after traversing 4 cm inside it. What velocity is needed for travelling distance of 9 cm in same block?
300 cm/s
As v2=u2−2as⇒u2=2as (∵v=0)⇒u2∝s⇒u2u1=(s2s1)1/2⇒u2=(94)1/2u2=32u1=300cm/s.