(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

2 trains approach each other on same track with equal speed of 20 m/s. When they are 2km apart, they see each other and deaccelerate. If deaccelerations are uniform, how large the acc. would be to avoid collision.

2. Relevant equations

[tex]v^{2} - v_{0}^{2} = 2ax [/tex]

3. The attempt at a solution

The book says that the 2 trains will stop at 1000m and and they find out acceleration by usual method to be -0.2m/s^{2}with velocity 20m/s and distance 1000m

But, I'm solving this problem by looking through a frame of reference going at -20m/s, so one of the trains appear to be stationary to me and the other moving with double velocity i.e. 40m/s. Then I calculate the acceleration which will stop this train in 2kms distance. Which comes out to be -0.4m/s^{2}, twice the answer.

Please guide me where I am wrong.

Thanks.

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# Homework Help: 2 trains colliding, where am I wrong?

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