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Homework Help: Another Physics Problem

  1. Jan 19, 2005 #1
    kay well here goes:

    An object moving with constant acceleration has a velocity v = 55.2m/s when it is at x = 6.9m and a v = 82.4m/s when it is at x = 12.4m. What is its acceleration?

    Now this problem qould be simple if time were given but it isn't so I'm gonna need a little bit of help please.

    What I did with this one was I plugged the numbers into the following equation:
    Vf^2 = Vi^2 +2a(xf - xi)

    which gave me,

    (82.4)^2 = (55.2)^2 + 2a(12.4 - 6.9)
    6789.76 - 3047.04 = 2a(5.5)
    a = 340.25m/s^2

    whish is needless to say, well....impossible. Is there another way to attack this problem or maybe if someone could please point out my mistake?
     
  2. jcsd
  3. Jan 19, 2005 #2
    That should be right.
     
  4. Jan 19, 2005 #3
    but it isn't! I submitted my answer (my h/w is done on the net) and it said it was incorrect. too hard!!!
     
  5. Jan 19, 2005 #4
    Hmm, let me think for a bit.
     
  6. Jan 19, 2005 #5
    thanks for taking the time! :)
     
  7. Jan 19, 2005 #6
    I don't know what's wrong, that answer should be right, maybe I missed something.
     
    Last edited by a moderator: Jan 19, 2005
  8. Jan 19, 2005 #7

    learningphysics

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    Can you double check the question? Maybe it was 55.2 m/s at 12.4m and 82.4 m/s at 6.9m?
     
  9. Jan 19, 2005 #8
    nope its right.

    and like its a three part question so I can't attempt the other two parts until i get the first one correct - maybe I'll try submitting it again (we get 3 tries before its marked as wrong)
     
  10. Jan 19, 2005 #9
    but can something accelerate that quickly? it seems like its accelerating a little too fast... hmmm
     
  11. Jan 19, 2005 #10

    learningphysics

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    Don't submit it yet! futbol got a different answer! How did you get 134.52? I get the same thing as sundrops: 340.25 m/s^2
     
  12. Jan 19, 2005 #11
    good thing I tried submitting again! I had too many digits in my answer - not the proper amount of sig figs I guess. So the answer is correct! [340.2] (man I hate computers *grumbles*)

    thanks to everyone who posted! :D
     
  13. Jan 19, 2005 #12
    wow! you guys are awesome - thanks again!
     
  14. Jan 19, 2005 #13
    Lol, you confused the hell out of me :P Time to get some rest now :P
     
  15. Jan 19, 2005 #14

    learningphysics

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    Cool! Yeesh, that's annoying though.
     
  16. Jan 19, 2005 #15
    g'nite futbol thanks again!
     
  17. Jan 19, 2005 #16
    it sure is! whatever happened to the good ol' days where h/w was done by hand - and marked by people!?!?! lol
     
  18. Jan 19, 2005 #17
    thanks again!
     
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