Question

For the situation shown below , determine the velocity of image (with respect to ground)

• A. $-2\text{m/s}$
• B. $+2\text{m/s}$
• C. $0\text{m/s}$
• D. $-5\text{m/s}$

Answer 1

The correct option is D $-5\text{m/s}$

Given,
Velocity of object, $V_0=+3\text{m/s}$
Velocity of mirror, $V_m=-1\text{m/s}$

Velocity of object with respect to mirror,
$V_{Om}=V_o-V_m$
$=+3-(-1)$
$=+4\text{m/s}$

In the direction normal to the mirror, Relative velocity of image with respect to mirror is equal to Relative velocity of object with respect to mirror.$$V_{Im}=-V_{Om}$$ $\Rightarrow V_{Im}=-(+4)=-4\text{m/s}$

Let the velocity of image with respect to ground is $V_I$.

Again applying concept of relative velocity,

$V_{Im}=V_I-V_m$

$\Rightarrow V_I=V_{Im}+V_m$

$\therefore V_I=-4-1=-5\text{m/s}$

Hence, option (d) is the correct answer.

Why this question: To understand the effect of velocity of mirror and object in horizontal direction, on the velocity of image.