A) 6 s
B) 5 s
C) 4 s
D) 3 s
Correct Answer: B
Solution :
The rotational energy \[\frac{1}{2}I{{\omega }^{2}}=750\,\,J\] \[\Rightarrow \] \[{{\omega }^{2}}=\frac{750\times 2}{2.4}=625\] \[\Rightarrow \] \[\omega =25\,\,rad/s\] \[\alpha =\frac{{{\omega }_{2}}-{{\omega }_{1}}}{t}\] \[\Rightarrow \] \[5=\frac{25-0}{t}\] \[\Rightarrow \] \[t=5s\]
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