Question

A plane mirror is placed along the x-axis facing negative y-axis. The mirror is fixed. A point object is moving with $3\hat{i}+4\hat{j}$ in front of the plane mirror. The relative velocity of image with respect to its object is

• A. $-8\hat{j}$
• B. $8\hat{j}$
• C. $3\hat{i}-4\hat{j}$
• D. $-6\hat{i}$

Answer 1

The correct option is A $-8\hat{j}$

Velocity of object, ${\overline{v}}_{ob}=3\hat{i}+4\hat{j}$
Velocity of image ${\overline{v}}_{image}=3\hat{i}-4\hat{j}$
Relative velocity of image with respect to its object ${\overline{v}}_{rel}={\overline{v}}_{image}-{\overline{v}}_{ob}=(3\hat{i}-4\hat{j})-(3\hat{i}+4\hat{j})=-8\hat{j}$