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STD 11 - 2. motion in straight line — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 11 - 2. motion in straight line4 Marks
MCQ
An express train is moving with a velocity $v_1$. Its driver finds another train is moving on the same track in the same direction with velocity $v_2$. To escape collision, driver applies a retardation a on the train. the minimum time of escaping collision will be
  • ✓
    $t = \frac{{{v_1} - {v_2}}}{a}$
  • B
    ${t_1} = \frac{{v_1^2 - v_2^2}}{2}$
  • C
    None
  • D
    Both
✓

Answer

Correct option: A.
$t = \frac{{{v_1} - {v_2}}}{a}$
a
(a) As the trains are moving in the same direction. So the initial relative speed $({v_1} - {v_2})$ and by applying retardation final relative speed becomes zero.

From $v = u - at$ $⇒$ $0 = ({v_1} - {v_2}) - at$ $⇒$ $t = \frac{{{v_1} - {v_2}}}{a}$

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