Two trains heading towards each other...?

Question

A red train traveling at 72km/h and a green train traveling at 144km/h are headed toward one another along a straight, level track. When they are 950m apart, each engineer sees the other's train and applies the brakes. The brakes slow each train at the rate of 1.0m/s^2. Is there a collision?

I've drawn myself a picture... I'm just not sure how I'd go abotu starting it. Could anyone give me a nudge in the right direction?

Answer 1

Closing velocity is 144+72 = 216 km/hr

Closing decelleration is 2 m/s2

distance is 950m

you can do this several ways, I'll calculate what the speed is at the end of 950 meters

d = ½at²

950 = ½(2)t²

t = 30.8 seconds

v = at = 2*30.8 = 61.6 m/s = 222 km/hr.

  since the velocity changed by 222 km/hr, and they started at 216, they stopped in time.

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Answer 2

Find the distance each travels using Vf^2 = Vi^2 + 2ad (where Vf is final velocity and Vi is initial velocity and a is acceleration or negative for deceleration and d is distance).  Add together and if they add to 950m (there is some conversion required) or greater there will be a collision.