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:

Options

A. `(1)/(10) m//s`
B. `(1)/(15) m//s`
C. `10 m//s`
D. `15 m//s`

Answer

B

Explanation

Mirror formula :
`(1)/(v)+(1)/(-280)=(1)/(20)`
`(1)/(v)+(1)/(20)+(1)/(280)`
`(1)/(v)+(14+1)/(280)`
`v=(280)/(15)`
`v_(1)=-((v)/(u))^(2).v_(om)`
`therefore v_(1)=-((280)/(15xx15))^(2).15`
`therefore v_(1)=(-15)/(15xx15)`
`v_(1)=-(1)/(15) m//s`