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Please help with an acceleration and distance problem

  1. Sep 17, 2008 #1
    1. The problem statement, all variables and given/known data
    A rocket sled goes down a track at a speed of 632 miles/hr. The sled is then brought to a rest in 1.40 seconds. Determine the a) negative acceleration experienced on the sled and b) the distance traveled during the negative acceleration.


    2. Relevant equations
    I attempted to calculate the acceleration using the a = change in velocity divided by change in time. The answer in my book was -202 meters/second squared, which i didn't understand because when I tried converting my result to met/sec, it did not match this. it was too much: -661.4 met/sec. i also tried calculating the distance traveled using the distance formula: x= xi + vit + 1/2 at^2 This also didn't work because I realized when I tried converting my answer to met/seconds, it was still way too much. The book's answer was 119 meters. My answer was 1, 495.2 meters. I thought that I used the correct formulas but there must be something I am missing.



    3. The attempt at a solution
    See above.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Sep 17, 2008 #2

    mgb_phys

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    Science Advisor
    Homework Helper

    Be carefull with signs!
    The equations are quite simple, v = u + at for the acceleration and v2 = u2 + 2as for the distance.
     
  4. Sep 17, 2008 #3
    ok thanks! i think i was not aware of a few of the simpler equations to use when solving these problems.
     
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