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Help with physical science problems

  1. Apr 7, 2005 #1
    Hey guys, i am doing some physical science and i was stuck on some problems. I was wondering if anyone could help me out. thanks so much!!

    1. Runner A is initially 5.8 km west of a flagpole and is running with a constant velocity of 8.2 km/h due east. Runner B is initialy 4.8 km east of the flagpole and is running with a constant velocity of 7.8 km/h due west. How far are the runners from the flagpole when their paths cross?

    2. While John is traveling along a straight interstate highway, he notices that the mile marker reads 252 km. John travels until he reaches the 149 km marker and then retraces his path to the 168 km marker. What is Johns resultant displacement from the 252 km marker?
  2. jcsd
  3. Apr 7, 2005 #2
    1. I would set up some equations and solve them:

    RA = -5.8km + 8.2km/h

    RB = 4.8 - 7.8km/h

    When they run into each other, they will both be at the same position, which means

    RA = RB

    -5.8km + 8.2km/h = 4.8 - 7.8km/h

    If the units are confusing you, try changing it to:

    8.2x-5.8 = -7.8x+4.8 and solve it for x.

    This will tell you how long they were running when they intersect.

    Take this and plug it into either one of the equations above, and find the distance the runner runs, then subtract that from his initial distance from the flagpole.

    I'm really drowsy so if this is really confusing im sorry.

    2. I already answered in your other post
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