Question

A plane mirror is placed along the $X$-axis facing negative $Y$-axis. The mirror is fixed. A point object is moving with $3 \hat{ i }+4 \hat{ j }$ infront 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. $-6 \hat{ j }$

Answer 1

Answer: (A)

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