InterviewSolution
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InterviewSolution
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A car is fitted with a convex side-view mirror of focal length 20 cm. A second car 2.8m behind the first car is overtaking the first car at a relative speed of 15 `m/s`. The speed of the image of the second car as seen in the mrror of the first one is:A. `10m//s`B. `15m//s`C. `1//10m//s`D. `1//15m//s` |
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Answer» Correct Answer - 2 `(1)/(v)+(1)/(u)=(1)/(f)` `-(1)/(v^(2))(dv)/(dt)-(1)/(u^(2))(du)/(dt)=0 rArr (dv)/(dt)=-(v^(2))/(u^(2))((du)/(dt))` `f=20cm` `(1)/(u)+(1)/(-280)=(1)/(20) rArr v=(280)/(15)cm` `v_(1)=-((280)/(15xx280))^(2)xx15 =(1)/(15)m//s` |
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