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Two trains travelling on the same track are approaching each other with equal speeds of 40m/s. The drivers of the train begin to decelerate simultaneously when they are just 2km apart. If the decelerations are both uniform and equal, then what is the value of deceleration to barely avoid collision?

The problem is based on collision, partly, as well as acceleration. According to it, I had tried using the third kinematic equation, but took the distance as 2km = 2000m, solving which I got the answer: 0.4. But, the answer to the problem was 0.8. So, I naturally thought about adding 0.4 with 0.4, but it isn't clear why. What do you think is wrong in the solution?

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  • $\begingroup$ we can use the concept of relative velocity.PS edit your question spelling of approaching are wrong $\endgroup$ – ragvri Feb 6 '15 at 11:16
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It basically means that they just need to cover half the distance. So, you have the distance to be covered, initial velocity(40) and final velocity has to be zero. Finding deceleration won't be an issue.

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