Question

two planes head towards each other with a speed v each. A particle which can produce elastic collision with either plane starts from the middle of the two planes with a speed 5v , when the separation between the planes is d. The total distance covered by the particle before the planes touch each other is:
a) 5d b) 10d c) 2.5d d) d

Answer 1

Time taken by two planes to touch each other = Distance / Relative Velocity
= d / 2v


Distance covered by particle = velocity of particle * time
= 5v * d/2v
= 2.5d

Option (c) is correct.