Question

Car B overtakes another car A at a relative speed of 40 ms^–1. How fast will the image of car B appear to move in the mirror of focal length 10 cm fitted in car A, when the car B is 1.9 m away from the car A?

(1) 4 ms^–1

(2) 0.2 ms^–1

(3) 40 ms^–1

(4) 0.1 ms^–1

Answer 1

 Correct Option is (4) 0.1 ms^–1

Mirror used is convex mirror (rear-view mirror)

\(\therefore\) Car will appear to move with speed 0.1 m/s.

Answer 2

m=f/f-u=1/200

v=m^2u=-1/400*40=-0.1m/s