Question

Two trains one of length 100 m and another of length 125 m, are moving in mutually opposite directions along parallel lines, meet each other, each with speed 10 m/s. If their acceleration are 0.3 m/s^2 and 0.2 m/s^2 respectively. Then time they take to pass each other will be

Answer 1

Answer:

10 secs

Explanation:

Given Two trains one of length 100 m and another of length 125 m, are moving in mutually opposite directions along parallel lines, meet each other, each with speed 10 m/s. If their acceleration are 0.3 m/s^2 and 0.2 m/s^2 respectively. Then time they take to pass each other will be

Now relative velocity of one train with respect to other is 10 + 10 = 20 m/s

Relative acceleration = 0.3 + 0.2 = 0.5 m / s^2

If trains cross each other , we know that

S = ut + ½ at^2

S = s1 + s2 = 100 + 125 = 225

So 225 = 20 t + 1/2 x 0.5 x t^2

   450 = 40 t + 0.5 t^2

   0.5 t^2 + 40 t – 450 = 0

  0.5 t^2 + 45 t – 5 t – 450 = 0

0.5 t(t + 90) – 5(t + 90) = 0

(0.5 t – 5) (t + 90) = 0

0.5 t – 5 = 0     t + 90 = 0

0.5 t = 5          t = - 90

 t = 10 secs taking positive value.

Time they take to pass each other will be 10 secs

Answer 2

Explanation:

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