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Homework Help: Determinging Acceleration and Distance

  1. Dec 12, 2011 #1
    If a rocket-powered sled is accelerated to a speed of 444 m/s in 1.8s, then what is the distance that the sled travels?

    So, my given:
    vf= 444 m/s
    t= 1.8 s

    I don 't know what equation to use to find distance. I tried:
    d=vi+1/2*at2 , but that didn't work. I just really don't know what equation to use. The answer should be 400m. Any help would be much appreciated.
     
  2. jcsd
  3. Dec 12, 2011 #2

    Delphi51

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    Homework Helper

    Knowing only the time and velocities, you must use a formula that has only three quantities - and use it to find the 3rd one. Ideally, you would use a constant accelerated motion formula with d,t,Vi, and Vf. If you can't find that one, use one to find the acceleration and then use d=vi+1/2*at2 to find the distance.

    There must be a list of constant accelerated motion formulas in your text book.
    The classic version is here: http://en.wikipedia.org/wiki/Equations_of_motion#Equations_of_uniformly_accelerated_linear_motion
     
  4. Dec 12, 2011 #3
    have yo tried A = (Vf - Vi) / T?
    once you have the acceleration value, the distance formula should work just fine
     
  5. Dec 12, 2011 #4
    Most of the time a sled would be accelerated from rest. If it isn't, it tells you the initial velocity.
     
  6. Dec 12, 2011 #5
    Need to find acceleration first and then plug its value into the correct equation that you stated.

    a = (v-u)/t = (444-0)/1.8 = 247m/s^2

    d = vi+1/2*at2

    = 0 + 1/2*247*1.8^2

    = 400m
     
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