First slide

Motion of centre of mass

Question

A bullet of mass m moving with velocity v strikes a block of mass Mat rest and gets embedded into it. The kinetic energy of the composite block will be

Easy

A

$\frac{1}{2} {mv}^{2} (\frac{m}{m + M})$
B

$\frac{1}{2} {mv}^{2} (\frac{M}{m + M})$
C

$\frac{1}{2} {mv}^{2} (\frac{M + m}{m})$
D

$\frac{1}{2} {mv}^{2} (\frac{M + m}{M})$

Solution

According to law of consecrations of momentum
$mv = (m + M) v^{'} where v^{'} = velocity of composite block ∴ V^{'} = (\frac{m}{M + m}) V K.E. of composite block = \frac{1}{2} (M + m) v^{' 2} ∴ K.E. = \frac{1}{2} (M + m) {(\frac{m}{M + m})}^{2} v^{2} = \frac{1}{2} {mv}^{2} [\frac{m}{M + m}]$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App