# Find the speed of the train.

1. Sep 19, 2015

### astrololo

1. The problem statement, all variables and given/known data
A train is at 0 m/s at the begining. It accelerates on a distance of 60 m, after it goes on a constant speed on the next 120 m and it finally decelerates on the next on 30 m and stops. The whole traject is 25 sec. Find the constant speed.

2. Relevant equations

x final = x initial + v initial * t + 1/2 * a * t^2
3. The attempt at a solution

60 = 0 + 0 + 1/2* a* t^2

60 = 1/2 * a * t^2

We also know that the first traject goes from 0 to 60 m and from 60 to 180 m and finally from 180 to 210 m.

2. Sep 19, 2015

### SteamKing

Staff Emeritus
Writing down a couple of equations is not a valid attempt at solution. For this problem, you must examine all the parts of the trip in order to determine the constant speed of the train.

3. Sep 19, 2015

### astrololo

Yeah I know but I have no idea on what to do next.... I wrote down 3 equations for each part of the traject but after that I have no idea...

4. Sep 19, 2015

### SteamKing

Staff Emeritus
You wrote down an equation covering the first part of the trip. Don't you think you should write some additional equations describing the other parts of the same trip?