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Question
Boy X is standing in front of a plane mirror while boy Y is running towards him from behind. If the boy Y is running at a speed of 1 m/s, how many metres nearer does the boy Y seem to be away from boy X after 5 seconds?
Boy X is standing in front of a plane mirror while boy Y is running towards him from behind. If the boy Y is running at a speed of 1 m/s, how many metres nearer does the boy Y seem to be away from boy X after 5 seconds?
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Solution
The correct option is D 5 m
If an object moves with a speed v towards (or away from) a plane mirror, the image of the object will also move with the same speed v towards (or away from) the mirror with respect to the mirror.
Therefore, the speed of the image of man Y w.r.t the mirror is 1 m/s.
So, in 5 seconds, the distance covered by Y’s image is 1 m/s × 5 s = 5 m toward the mirror as man Y approaches the mirror.
In other words, Y’s image is moved 5 m towards man X. Therefore, man Y seems to be away 5 metres nearer from man X after 5 seconds.
If an object moves with a speed v towards (or away from) a plane mirror, the image of the object will also move with the same speed v towards (or away from) the mirror with respect to the mirror.
Therefore, the speed of the image of man Y w.r.t the mirror is 1 m/s.
So, in 5 seconds, the distance covered by Y’s image is 1 m/s × 5 s = 5 m toward the mirror as man Y approaches the mirror.
In other words, Y’s image is moved 5 m towards man X. Therefore, man Y seems to be away 5 metres nearer from man X after 5 seconds.
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