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Stuck on this simple physics problem.

  1. Sep 21, 2010 #1
    1. The problem statement, all variables and given/known data

    Two buses are moving at constant speeds, in the same direction, the first at 42 km/h and the second at 54 km/h. They are 18 km apart. How long will it take the second bus to catch up to the first? (4 marks)


    2. Relevant equations

    average velocity = d/t

    3. The attempt at a solution

    Ok well first I tried to make a table of the graph but then I remembered that they were 18 km apart so then I had to rethink and I'm still really stuck on this.
     
  2. jcsd
  3. Sep 21, 2010 #2

    rl.bhat

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    Homework Helper

    When they catch up, the first bus moves through x km and second bus moves through x + 18 km, and they must have taken the same time to cover that distance.

    Can you proceed now?
     
  4. Sep 21, 2010 #3
    What would be a formula that could solve for this?

    Or do I have to use a table?
     
  5. Sep 21, 2010 #4

    rl.bhat

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    Homework Helper

    Velocity = x/t. So t = x/v.

    Since t is the same

    x/v1 = (x+18)/v2

    v1 and v2 are given. Solve for x.
     
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