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Homework Help: Simple? Motion Equation Problems

  1. Sep 22, 2013 #1
    1. The problem statement, all variables and given/known data

    1. A soccer player with an initial velocity of 0 (rest position) accelerates uniformly as she runs down the field travelling 17m [E] in 3.8s. What is her final velocity?

    2. A skier sits at rest on top of a hill. If the skier travels 70m [down] in 5.3s while accelerating uniformly, what acceleration does he experience?

    2. Relevant equations

    a = (vf-vi)/t ?

    3. The attempt at a solution

    So I used the above equation to try and solve these but they're not working?
    The answer to 1 is supposed to be 8.9m/s[E] and the answer to 2 is 5.0m/s2 [down].
  2. jcsd
  3. Sep 22, 2013 #2
    You are not given the final velocity in this problem. Obviously, the equation you listed as relevant is not applicable. You need another equation. Examine carefully what is given in the problem and find an appropriate equation.
  4. Sep 22, 2013 #3
    yes, but if i isolate vf and i get vf = vi +at, shouldn't that be ok to use?
  5. Sep 22, 2013 #4
    Acceleration is not given either.
  6. Sep 22, 2013 #5
    oh; d= (vf+vi)/2t
    okay i got it, thank you :)
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