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Homework Help: Position, velcity, and time

  1. Feb 10, 2008 #1
    1. The problem statement, all variables and given/known data
    A plane takes off from San Francisco to New york (4600km) at 1100km/h. At the same time, another plane takes off from New York to San Franscisco at 700km/h. When do the two planes pass each other?

    Can you please help me in this problem?
    I tried finding the psosition function of the two planes and equating them in order to find the time, but I found the time negative, which doesn't make much sense.

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Feb 10, 2008 #2
    Well, you could go about this in a couple of different ways.

    Firstly, there are two planes which must travel a combined distance of 4600 Km, you could consider one plane travelling that same distance at 1100 + 700 = 1800 Km/h. That would give you the time until they meet.

    Secondly, you could consider their speeds to be a ratio of the distances they travel. For example, plane A travels 1100 / (1100 + 700) of the distance before meeting plane B. You can multiply that fraction by 4600 to calculate the distance, then based on it's speed calculate the time it would take. Similarly plane B travels 700 / (1100 + 700) of the distance.
  4. Feb 10, 2008 #3
    Thanks a lot...YOU SAVED MY LIFE.....I got everything you said ;)
  5. Feb 10, 2008 #4
    Happy to help. :smile:
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