# Homework Help: Can the passenger catch the train if the platform is long enough?

1. Nov 20, 2005

### cocoavi

Mmmm if it's not too much of a problem could someone help me with the following question?:

A late passenger sprinting at 8.0m/s is 30.0m away from the rear end of a train when it starts out of the station with an acceleration of 1.0m/s^2. Can the passenger catch the train if the platform is long enough?

THX!

2. Nov 20, 2005

### lightgrav

well, he's pretty far from it, but already going fast. The train's not too quick.

3. Nov 20, 2005

### cocoavi

I'm sorry I know I should be telling what I've already done.. but I just don't think I'm doing it right and I've just been taking random equations and working on them..~ well.. I did d=vit + 0.5at^2 + 30... to make d=0.5t^2 +30 for the train.. but I have no idea why I did that T_T..

4. Nov 20, 2005

### lightgrav

there are several ways to answer this question, each approach valid, so
we want to "guide" you in an approach that "makes sense" to you already.

If you try to catch a train (or anything else!) it is nice to know where it is.
It is also nice to know where YOU are. So, where is this fast runner?

5. Nov 20, 2005

### dx

Try rephrasing the question. It asks you whether the passenger can catch the train. That is equivalent to asking if at any time the positions of the passenger and the train are the same. So, now you know what to do. You must write both the positions as functions of time. How does the position of both the passengers depend on time? Is there any value of t for which both the functions give the same position?