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Homework Help: Distance and Time (Having a Mental Block.

  1. Oct 4, 2009 #1
    1. The problem statement, all variables and given/known data
    Car A leaves school when a clock reads 0.0s and travels at 65 km/h. Car B traveling at 90 km/h leaves from a convenience store +10 km away from the school and 15 minutes later than Car A.

    a.) What is the displacement of each car after 1.5 hrs.

    b.) The two cars pass a gas station at 115 km from the school. When did each car pass the station?

    2. Relevant equations


    3. The attempt at a solution
    I am in a mental block at the moment. I have asked about a problem earlier today on the forums and I been on a roll with the homework ever since. But now I have reached a mental block on the very last problem. I am beginner at physics. Just taught myself the basics today. I've done a few dozen problems that were assigned for homework and had little problem with them.
    Would someone be as kind as to descriptively explain to me on how to do this problem. I really want to learn on how to do well in physics, so any tips would be greatly appreciated also. Thanks in advance to all those who took the time to read and/or answer this post.
  2. jcsd
  3. Oct 4, 2009 #2


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    Homework Helper

    Yes, a complicated problem. I would deal with the units first. You probably don't want to change the km/h, so do change that 15 minutes into .25 hour so everything is in km and hours.
    For this one you must write a d=vt equation for each car, keeping in mind that the time for the second car starts 15 minutes later, so its "t" will be written "T-.25". Keep "T" to mean the time from when the first car leaves. It isn't clear whether the second car has 10 less or 10 more km to go, so you may want to keep both possibilities in mind. Make "D" stand for the distance from the school in both cases. Once you have your two equations, you can use them to answer the questions.
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