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Homework Help: Total distance

  1. Sep 23, 2004 #1
    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. jcsd
  3. Sep 23, 2004 #2


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    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.
  4. Sep 23, 2004 #3


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    What approaches have you tried?
  5. Sep 23, 2004 #4
    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 :)

  6. Sep 23, 2004 #5
    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?
  7. Sep 23, 2004 #6
    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. :wink:

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