How Far Does a Slowing Train Travel?

[lvck]

Homework Statement

1. A train moving at a speed of 30 m/s slows down to 10m/s in 30s. How far had the train gone before it's speed was reduced from 30m/s to 20 m/s?

Homework Equations

D= Vi times T + at(squared) divide it by 2

The Attempt at a Solution

None yet. Please help me with the solution

 

[LowlyPion]

Welcome to PF.

Consider a different equation:

Vf² = Vi² + 2*a*x

For other useful kinematic equations see:
https://www.physicsforums.com/showpost.php?p=905663&postcount=2

 

[lvck]

Honestly I am having a hard time figuring out what the initial velocity is.. and the acceleration

 

[LowlyPion]

You can figure the "a" simply by using the relationship that ΔV = a*t That Δ v is (10 - 30) = -20 = a*t

Using the V² = ... formula then your final speed is 10 m/s and you Initial is 30 and your acceleration is negative because it's slowing you down to 20, then you can figure x.