A) \[1.2\times {{10}^{5}}k-cal\]
B) \[2.4\times {{10}^{5}}k-cal\]
C) \[4.8\times {{10}^{5}}k-cal\]
D) \[6\times {{10}^{5}}k-cal\]
Correct Answer: B
Solution :
The kinetic energy of train\[=\frac{1}{2}m{{v}^{2}}\] \[=\frac{1}{2}\times 5\times {{10}^{6}}\times {{\left( \frac{72\times 5}{18} \right)}^{2}}\] \[=1\times {{10}^{9}}J\] This energy change to heat \[\therefore \]Heat\[(Q)=\frac{1\times {{10}^{9}}}{4.2\times {{10}^{3}}}\] \[=2.4\times {{10}^{5}}k\,cal\]
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