Question

Two trains, which are moving along different tracks in opposite directions, are put on the same track due to a mistake. Their drivers, on noticing the mistake, start slowing down the trains when the trains are $300m$ apart. Graphs given below show their velocities as function of time as the trains slow down. The separation between the trains when both have stopped is

• A. 120 m
• B. 280 m
• C. 60 m
• D. 20 m

Answer 1

Answer: (D)

Initial distance between trains is $300m$.
Displacements of trains can be calculated by area under $V-t$ graph.

Displacement of train $1=\frac{1}{2}\times 10\times 40$
$=200m$
Displacement of train $2=\frac{1}{2}\times 8\times (-20)$
$=-80m$
which means it moves towards left.
$\therefore$ Distance between the two is
$300-200-80=20m$.