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JEE Main 20202 SeptemberMorning Shift
Exam
JEE Main
Year
2020
Date
2 September
Shift
Morning Shift
Subject
Physics
Chapter
Motion in One Dimension

JEE Main 2020 · 2 September · Morning Shift · Physics · Motion in One Dimension

Train A and train B are running on parallel tracks in the opposite...

Train AA and train BB are running on parallel tracks in the opposite directions with speed of 36kmhour−1and72kmhour−136km{hour}^{- 1} and 72km{hour}^{- 1}, respectively. A person is walking in train AA in the direction opposite to its motion with a speed of 1.8kmhour−11 . 8km{hour}^{- 1}. Speed (inms−1)\left(inm{s}^{- 1}\right) of this person as observed from train BB will be close to: (take the distance between the tracks as negligible)

Options

  1. A29.5ms−129 . 5m{s}^{- 1}
  2. B28.5ms−128 . 5m{s}^{- 1}
  3. C31.5ms−131 . 5m{s}^{- 1}
  4. D30.5ms−130 . 5m{s}^{- 1}

Correct answer

A. 29.5ms−129 . 5m{s}^{- 1}

Step-by-step solution

VMA=−1.8kmhr−1=−0.5ms−1\begin{array}{ll}{V}_{MA} = - 1 . 8km{hr}^{- 1} = - 0 . 5m{s}^{- 1}\end{array}

Vman,B=Vman,A+VA,B\begin{array}{ll}{V}_{man}, B = {V}_{man}, A + {V}_{A}, B\end{array}

=Vman,A+VA−VB\begin{array}{ll}= {V}_{man , A} + {V}_{A} - {V}_{B}\end{array}

=−0.5+10−(−20)\begin{array}{ll}= - 0 . 5 + 10 - ( - 20 )\end{array}

=−0.5+30= - 0 . 5 + 30

=29.5ms−1= 29 . 5m{s}^{- 1}

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