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How many seconds will it take before the cars meet?

  1. Sep 1, 2015 #1
    1. The problem statement, all variables and given/known data
    Two cars are initially 17.50 km apart on a straight road. If the cars are moving toward each other, car 1 with a speed of 7.50 m/s and car 2 with a speed of 10.40 m/s, how many seconds will it take before the cars meet? Round your answer to three significant figures.

    2. Relevant equations
    Don't know

    3. The attempt at a solution
    Converted to 17,500 m for the distance apart.
    I added 7.50 and 10.40; Then I divided 17,500 by 17.9 seconds
    =977.65 seconds
     
  2. jcsd
  3. Sep 2, 2015 #2

    Bystander

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    You have doubts? Need an organizing/systematic principle?
     
  4. Sep 2, 2015 #3
    I wanted to see if it was right because I didn't use any formulas, I just kinda thought about it.
     
  5. Sep 2, 2015 #4

    haruspex

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    You have one typo, you wrote 17.9 seconds instead of 17.9 m/s.
    If you want to relate your method to a principle, it would be that of relative velocity. Or, equivalently, a change to a different inertial reference frame.
     
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