Question

What is the velocity (in cm/s) of image in situation shown below? Object moves with velocity 10 cm/s and mirror moves with velocity 2 cm/s as shown.

• A. 2 cm/s
• B. 0 cm/s
• C. 4 cm/s
• D. 1 cm/s

Answer 1

The correct option is B 0 cm/s

In the mirror frame of reference,

$v_0=8cm/s$
$v_i=-{\left(\frac{v}{u}\right)}^2{v}_0$
$=-{\left(\frac{f}{f-u}\right)}^2{v}_0=-(\frac{10}{10+10}{)}^2\times v_0$
$=-\left(\frac{1}{4}\right)\times 8$
$=-2cm/s$

So with respect to ground, speed of image

$v_i^{\prime }=-2+2=0cm/s$