A) 10 s
B) 8 s
C) 7 s
D) 5 s
Correct Answer: A
Solution :
The acceleration produced in the car \[ma=\mu R\] \[\Rightarrow \] \[ma=\mu \,mg\] \[\Rightarrow \] \[a=\mu g=1\times 10\,m\text{/}{{s}^{2}}=10\,m\text{/}{{s}^{2}}\] For crossing of the bridge in minimum time, it has to travel with maximum acceleration. Here, \[u=0,\,s=500\,m\] \[a=10\,m\text{/}{{s}^{2}}\] From equation \[s=ut+\frac{1}{2}a{{t}^{2}}\]we have, \[500=0\times t+\frac{1}{2}\times 10\times {{t}^{2}}\] \[\Rightarrow \] \[{{t}^{2}}=100\Rightarrow t=10\,s\]
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