# Homework Help: Total distance

1. Sep 23, 2004

### hytuoc

Plz help me w/ this problem...thanks
Two trains, each hav ing a speed of 30 km/h, are headed at each other on the same straight track. A bird that can fly 60km/h flies off the front of one train when they r 60km apart and heads directly for the other train. On reaching the other train it flies directly back to the first train, n so forth. What is the total distance the bird travels?

2. Sep 23, 2004

### pervect

Staff Emeritus
I think you need to give more information, like how far apart the trains are. Here's a hint, figure out the amount of time the bird is aloft first.

3. Sep 23, 2004

### Tide

What approaches have you tried?

4. Sep 23, 2004

### DrWarezz

Like pervect said, you need to specify the initial distance between the two trains.

Also: you say that the bird can fly 60km/h. Do you mean to say '60km/h' added onto the trains velocity? Or, due to it's size and shape, can only reach 60km/h at the max, due to air resistance? In which casem the factor of Frame of reference comes into play.

So, specify whether the birds velocity is 60km/h relative to the ground, or the train, also, the initial distance between the trains :)

[r.D]

5. Sep 23, 2004

### vsage

The other guys said it right. It wasn't specified whether the bird can go 60k/h with respect to the ground or the train it left from but I'll assume with respect to the ground. If both trains are heading toward each other at 30k/h, it will take them one hour to meet correct? If the bird flies as fast as possible in one hour, how far could it have gone?

6. Sep 23, 2004

### recon

A similar question was asked on PF several months ago. You can access it here: https://www.physicsforums.com/archive/t-21453_Tips_for_problem.html.

Lets not confuse hytuoc with relative velocity, okay? I don't think this problem would be so conjugated. Since we are on this topic, I would also like to say that the length of the bird's body is not specified. Hence, the problem cannot be solved unless we assume the bird to be a 1D object, which is an impossible situation.

hytuoc, ignore what we have all just said if you confused, and just click on my link above.