QJEEM11Ph0304: JEE Main 2011 Physics - Class 12 JEEM11Ph0304 Solution: A car is fitted with a convex side-view mirror of focal length…

Question

Verified Solution • 2025–26 Session moderate

A car is fitted with a convex side-view mirror of focal length

20

c m

. A second car

2.8 m

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 mirror of the first one is :

Accepted Answer

From mirror formula

\frac{1}{v} + \frac{1}{u} = \frac{1}{f}

so,

\frac{d v}{d t} = - \frac{v^{2}}{u^{2}} (\frac{d u}{d t})

\Rightarrow \frac{d v}{d t} = - {(\frac{f}{u - f})}^{2} \frac{d u}{d t}

\Rightarrow \frac{d v}{d t} = \frac{1}{15} m / s

Step-by-Step Verified Solution