A) 2 kg
B) 1.2 kg
C) 3 kg
D) 1.5 kg
E) 1 kg
Correct Answer: B
Solution :
Conservation of linear momentum gives \[{{m}_{1}}{{u}_{1}}+{{m}_{2}}{{u}_{2}}={{m}_{1}}{{v}_{1}}+{{m}_{2}}{{v}_{2}}\] \[\Rightarrow \] \[{{m}_{2}}{{v}_{2}}=\frac{3u}{2}\] ?? (1) Conservation of kinetic energy gives \[\frac{1}{2}{{m}_{1}}u_{1}^{2}+\frac{1}{2}{{m}_{2}}u_{2}^{2}=\frac{1}{2}{{m}_{1}}v_{1}^{2}+\frac{1}{2}{{m}_{2}}v_{2}^{2}\] \[\Rightarrow \] \[{{m}_{2}}v_{2}^{2}=\frac{15{{u}^{2}}}{8}\] ...(2) Hence, on solving Eqs. (1) and (2), we get \[{{m}_{2}}=1.2\,kg\]
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