Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Word Problem.Is this correct?

  1. Feb 21, 2009 #1
    ....got it....

    Thnx though!
     
    Last edited: Feb 22, 2009
  2. jcsd
  3. Feb 22, 2009 #2
    Check this out.

    x: person's x position
    y: person's y position
    X: raptor's x position
    Y: raptor's y position

    x = 5(sqrt2) (t+3)
    y = 5(sqrt2) (t+3)

    X = 12(sqrt2) t_x
    Y = 12(sqrt2) t_y

    If the raptor wants to catch you, t_x must equal t_y... because the person is on the line x=y and the raptor starts at the origin. So t_x equals t_y equals t.

    Let T represent the time the raptor catches you (with t = 0 being when the raptor starts running). Then we must have that

    5(sqrt2)(T+3) = 12(sqrt2)(T/2)

    The equation is the same for y.

    Solving for T...

    5T + 15 = 6T

    T = 15.

    So it takes the raptor 15 seconds to catch the dude.

    It can't very well be 1.5 s, can it? The raptor has only moved 22.5(sqrt2) = 32 total, while the person has moved 45 total. Even if the raptor was chasing the guy directly, he wouldn't catch him.
     
  4. Feb 22, 2009 #3
    Comparing my solution with yours(the one that i did after my first post), i see that we have the same idea, in general terms with some slight differences, besides that you have a typo on your solution, because the speed of the raptor is 15sqrt{2}m/s and not 12sqrt{2}m/s so the final answer should be 6 s.

    Cheers!
     
  5. Feb 22, 2009 #4

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    What happened? Did the raptor eat your post instead of you??
     
  6. Feb 22, 2009 #5
    It looks like that's the case.

    Well, in fact, after i initially posted the problem and the 'solution', after a few hours i wanted to edit it since i found the correct solution, but while tring to post it the pf was having trouble or don't know what, so that's what was left from my post.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Word Problem.Is this correct?
  1. Is this correct? (Replies: 3)

  2. Word Problem (Replies: 8)

  3. Origin of the word? (Replies: 1)

Loading...