Question

Body A of mass 4m moving with speed u collides with another body B of mass 2m, at rest. The collision is head on and elastic in nature. After the collision the fraction of energy lost by the colliding body A is :

• A. $\frac{4}{9}$
• B. $\frac{5}{9}$
• C. $\frac{1}{9}$
• D. $\frac{8}{9}$

Answer 1

The Correct Option is D

Fractional loss of KE of ccolliding body
$\frac{\Delta KE}{KE} = \frac{4\left(m_{1}m_{2}\right)}{\left(m_{1} + m_{2}\right)^{2}} $
$ = \frac{4\left(4m\right)2m}{\left(4m+2m\right)^{2}} $
$ = \frac{32m^{2} }{36m^{2}} = \frac{8}{9} $