A) 36 J
B) 18 J
C) 9 J
D) 3 J
Correct Answer: B
Solution :
Common velocity \[=\frac{{{m}_{1}}{{v}_{1}}+{{m}_{2}}{{v}_{2}}}{{{m}_{1}}+{{m}_{2}}}\] \[=\frac{2\times 6+2\times 0}{2+2}\]\[=3m\text{/}s\] Initial kinetic energy \[=\frac{1}{2}{{m}_{1}}v_{1}^{2}+\frac{1}{2}{{m}_{2}}v_{2}^{2}\] \[=\frac{1}{2}\times 2\times {{(6)}^{2}}\] = 36 J Final kinetic energy\[=\frac{1}{2}({{m}_{1}}+{{m}_{2}}){{v}^{2}}\] \[=\frac{1}{2}(2+2){{(3)}^{2}}=18J\] The amount of heat evolved \[={{E}_{1}}-{{E}_{2}}\] = 36 ? 18 = 18J
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