Question

A boy moves with the speed of 10m/s towards the stationary plane mirror and the boy see his image in the plane mirror the speed at which image of the boy appear to approach the boy is found to be 10km/s. What is the value of k

Answer 1

Velocity of boy(Vb)= 10 m/s
velocity of image (Vi)=-10 m/s
(-ve sign is there as its direction is opposite to that of the boy)

Relative speed between boy and image =

Vb-Vi=10-(-10)=10+10=20 m/s

So the image will approach him at 20 m/s.