A) \[2\,km/h\]
B) \[4\,km/h\]
C) \[2\,km/h\]
D) \[8\,km/h\]
Correct Answer: D
Solution :
Given equation \[s={{t}^{2}}-2t\] .....(i) and \[\frac{ds}{dt}=\]velocity \[\frac{dS}{dt}=8\pi r\frac{dr}{dt}=\frac{8\pi .7.5}{28\pi }=10\,c{{m}^{2}}/\min \] .....(ii) Put \[s=15\] in (i), we get \[{{t}^{2}}-2t-15=0\] or \[(t-5)(t+3)=0\] \[\therefore t=5\] Hence velocity of car \[=v=2(5)-2=8\,\,km/h\].You need to login to perform this action.
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