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What should I be thinking about to solve Uniform Motion Problems?

  1. Jan 31, 2009 #1
    1. The problem statement, all variables and given/known data

    A helicopter traveling 130 mph overtakes a speeding car traveling 80 mph. The car had a 0.5-hour head start. How far from the starting point does the helicopter overtake the car?

    The answer is 104 miles from the starting point.

    2. Relevant equations

    No equations were given, but the book told me to use charts similar to this:

    ...................Rate.....*.....Time.........=Distance (d)
    Helicopter......70................t............= 70t
    Plane.............500............2-t...........= 500(2-t)


    3. The attempt at a solution

    I ended up figuring it out, but world problems like these are still very fuzzy for me. My first attempt went something like this:

    Helicopter: 130 * ___ = ___
    Car:...........80 * 0.5 = 40 mi

    I just don't know what to think properly...
     
  2. jcsd
  3. Jan 31, 2009 #2

    Mk

    User Avatar

    You might say x = vt + .5a(t^2), correct?
    Use this equation to describe the motion of both the car and the helicopter and maybe you'll be able to figure out how to solve it on your own :smile: In the case of the car, use (t+0.5).
    Hint: Let t remain unknown so you can set the equations to equal each other.
    Also, make sure you post this next time in Introductory Physics, not precalculus mathematics.
     
    Last edited: Feb 1, 2009
  4. Feb 1, 2009 #3
    Hey, thanks for the hint and sorry for the rush of a post. I didn't bother to read the forum descriptions...

    And back to the question, that's what always got me stuck. I did found out how you had to add the heli's time onto the car, but I always got stuck on how to write the equation.
     
  5. Feb 1, 2009 #4

    Mark44

    Staff: Mentor

    No, not at all. As stated in title, this is uniform motion, so the .5 at^2 term is not relevant in this problem.
    IMO, this problem could reasonably be posted in either place.
     
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