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

Answer: (A)

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