Question

A bullet loses 2/3 of its velocity in penetrating 4 cm through a piece of wood. what more distance it can penetrate further.​

Answer 1

Answer:

Correct option is

C

1.0 cm

Case I :

[2u]2−u2=2.a.3

or −43u2=2.a.3⇒a=−8u2

Case II :

0−[2u]2=2.a.x or −4u2=2[−8u2]×x

⇒x=1cm

Alternative method : Let K be the initial energy and F be the resistive force. Then according to work-energy theorem,

W=ΔK

i.e., 3F=21mv2−21m[2v]2

      3F=21mv2[1−41]

      3F=43[