How Far Will a Uniformly Accelerating Train Travel Before Stopping?

[Phyzics J]

Can Someone help me with this constant acceleration problem?! pleasez

1. A train which is moving with uniform acceleration is observed to take 20s and 30s, respectively, to travel successive 400m. How much farther will it travel vefore coming to rest if the acceleration remains constant?



2. I tried to find the change in velocity between those time intervals by using the formula:
Velocity=change in displacement/time

The Attempt at a Solution

 

[rl.bhat]

Hi Phyzics J, welcome to PF.
Let vo be the initial velocity when you start observing the train.
Then use
s = vo*t -1/2*a*t^2 and write two equations. One for s = 400 m and t = 20 sand second for s = 400 + 400 = 800 m and t = 20 + 30 = 50 s.
Solve the two equations to find vo and a and proceed.

 

[Phyzics J]

Thank you sooo much rl.bhat, I appreciate it :)