A) 256 J
B) 486 J
C) 524 J
D) 324 J
Correct Answer: B
Solution :
Applying conservation of linear momentum, write,\[{{m}_{1}}{{u}_{1}}={{m}_{2}}{{u}_{2}}\] Here \[{{m}_{1}}=18\,kg,\,{{m}_{2}}=12\,kg\] \[{{u}_{1}}=6\,m{{s}^{-1}},{{u}_{2}}=?\] \[\therefore \]\[18\times 16=12{{u}_{2}}\] \[\Rightarrow \]\[{{u}_{2}}=\frac{18\times 6}{12}=9\,m{{s}^{-1}}\] Thus, kinetic energy of 12 kg mass \[{{K}_{2}}=\frac{1}{2}{{m}_{2}}u_{2}^{2}=\frac{1}{2}\times 12\times {{(9)}^{2}}\] \[=6\times 81=486\,J\]
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