Two trains, each $40 \mathrm{~m}$ long are travelling in opposite direction with equal velocity $20…

Two trains, each $40 \mathrm{~m}$ long are travelling in opposite direction with equal velocity $20 \mathrm{~m} / \mathrm{s}$. The time of crossing is
  1. $1 \mathrm{~s}$
  2. $2 \mathrm{~s}$
  3. $3 \mathrm{~s}$
  4. Zero

Solution

Time $=\frac{\text { total length }}{\text { relative velocity }}=\frac{\mathrm{X}+\mathrm{X}}{20+20}=\frac{2 \mathrm{X}}{40} \mathrm{~s}$
$=2 \mathrm{~s}$

Asked in: JEE Mains - Motion In One Dimension - Test 4

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