An object moving towards mirror as shown in the figure.
A. the speed of image will be 2 m/s irrespective the speed of mirror.
B. the speed of image will be 2 m/s only when speed of mirror is zero.
C. the speed of image will be 6 m/s when mirror is moving towards object with 2 m/s.
D. the speed of image will be 6 m/s, where mirror is moving away from object with 2 m/s.
E. the speed of image will be 2 m/s, where mirror is moving away from object with 2 m/s.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → B, C, E only
Use the relation for velocity of image in a plane mirror:
$v_I = 2v_M - v_O$
Take right direction as positive.
Object is moving towards mirror $\rightarrow v_O = +2 \text{ m/s}$
A: Image speed always 2 m/s: Depends on mirror motion $\rightarrow$ . Incorrect
B: Mirror at rest $v_M = 0$
$v_I = 2(0) - 2 = -2$
Speed = $2 \text{ m/s}$ Correct
C: Mirror moving towards object $v_M = -2$
$v_I = 2(-2) - 2 = -6$
Speed = $6 \text{ m/s}$ Correct
D: Mirror moving away $v_M = +2$
$v_I = 2(2) - 2 = 2$
Speed = $2 \text{ m/s}$ (not 6)
E: Mirror moving away $v_M = +2$
$v_I = 2$
Speed = $2 \text{ m/s}$ Correct