Question

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

• A. 1 cm
• B. 2 cm
• C. 3 cm
• D. 4 cm

Answer 1

The correct option is A 1 cm

For 1st part of its motion,

Let initial vel. = u
$\therefore finalvel=\frac{u}{2}s=3cm$
$\therefore (\frac{u}{2}{)}^2-u^2=2.a.3\Rightarrow a=-\frac{u^2}{8}$
For 2nd part of its motion,
$Initialvel=\frac{u}{2};finalvel=0;a=-\frac{u^2}{8}$
$\therefore 0-\frac{u^2}{4}=-2\times \frac{u^2}{8}\times x\Rightarrow x=1cm$