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JEE Main 2019 (12 Jan, Shift 1) · Relative Velocity

Relative Velocity question from JEE Main 2019 (12 Jan, Shift 1)

Q9JEE Main 2019 · 12 JAN · SHIFT 1Medium

Relative Velocity

A passenger train of length 60 m travels at a speed of 80 km/hr. Another freight train of length 120 m travels at a speed of 30 km/hr. The ratio of times taken by the passenger train to completely cross the freight train when: (i) they are moving in the same direction, and (ii) in the opposite direction is:

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Answer: (c)

  1. Distance to cross completely =60+120=180 m= 60 + 120 = 180\text{ m} in both cases.
  2. Same direction: vrel=80−30=50 km/hv_{rel} = 80 - 30 = 50\text{ km/h}; opposite: vrel=80+30=110 km/hv_{rel} = 80 + 30 = 110\text{ km/h}
  3. t1t2=11050=115\frac{t_1}{t_2} = \frac{110}{50} = \frac{11}{5}
  4. So the answer is (c) 115\frac{11}{5}.
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