InterviewSolution
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InterviewSolution
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A particle starts from rest and traverses a distance l with uniform acceleration, then moves uniformly over a further distance 2l and finally comes to rest after moving a further distance 3l under uniform retardation. Assuming entire motion to be rectilinear motion the ratio of average speed over the journey to the maximum speed on its ways isA. `1//5`B. `2//5`C. `3//5`D. `4//5` |
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Answer» Correct Answer - C Let `upsilon_(m)` be the maximum speed, `upsilon_(m)=a_(1)t_(1)` and `upsilon_(m) = sqret(2a_(1)l) " " (because u = 0)` `t_(2)=(2l)/(upsilon_(m))` and `upsilon_(m)=a_(2)t_(3)=sqrt(2a_(2)(3l))` Now, average speed, `upsilon_(av)=(l+2l+3l)/(t_(1)+t_(2)+t_(3))` `upsilon_(av)=(6l)/((upsilon_(m)//a_(1))+(2l//upsilon_(m))+(upsilon_(m)//a_(2)))` `=(6l)/(((upsilon_(m))/(upsilon_(m)^(2)//2l))+((2l)/(upsilon_(m)))+((upsilon_(m))/(upsilon_(m)^(2)//6l)))` `=(6l)/((10l//upsilon_(m)))=(3upsilon_(m))/(5)` `rArr (upsilon_(av))/(upsilon_(m))=(3)/(5)` |
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