question_answer

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 300 m 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

Correct Answer: D

Solution :

[d] Initial distance between trains is 300 m. displacements of trains can be calculated by area under V-t graph. Displacement of train 1=\[1=\frac{1}{2}\times 10\times 40=200m\] Dispacement of train\[2=\frac{1}{2}\times 8\times (-20)=-80m\] Which means it moves towards left. \[\therefore \] Distance between the two is 300-200-80-20 m.