# Homework Help: Train collision problem, speed at impact

1. Oct 1, 2009

### kazo0

1. A red train traveling at 72 km/h and a green train traveling at 144 km/h are headed toward each other along a straight, level track. When they are 950 m apart, each engineer sees the other’s train and applies the brakes. The brakes slow each train at the rate of 1.0 m/s2. Is there a collision? If so, answer yes and give the speed of the red train and the speed of the green train at impact, respectively. If not, answer no and give the separation between the trains when they stop.

I was able to find that the trains would indeed collide, I don't know how to find out the last part, what their speeds are at the instant that they collide. Can anyone help me out?

Thanks

2. Relevant equations
i used the equation V^2 = Vo^2 + 2((delta)x)

3. The attempt at a solution
I was able to find that the trains would indeed collide, I don't know how to find out the last part, what their speeds are at the instant that they collide. Can anyone help me out?

Thanks

2. Oct 1, 2009

### Delphi51

Write equations for the distance each train travels up to time t after the brakes are applied. By setting the total of the two distances to 950 m, you should be able to solve for the time of the collision. Then you can use velocity formulas for the two trains to find their speeds at that time.