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Homework Help: Newton's Laws

  1. Sep 17, 2010 #1
    1. The problem statement, all variables and given/known data

    A 5.0kg salmon is weighed by hanging it from a fish scale attached to the ceiling of an elevator. What is the apparent weight of the salmon if the elevator is (a) at rest, (b) moving upward at 2.5 m/s2, and (c) moving downward at 3.2 m/s2?

    2. Relevant equations

    Sum of F = 0
    F(t) - W = 0
    F(t) = W

    Sum of F = Ma
    F(t) - W = Ma (W=mg)

    F(t)<W Sum of F = Ma
    W- F(t) = Ma

    3. The attempt at a solution

    i have trouble thinking out of the box to get the problem started. this is my very first time ever taking physics and i have not had a math or science class in a year. can anyone help me get started?! I would appreciate any help! Thank you!
  2. jcsd
  3. Sep 17, 2010 #2
    Part 1, you are correct. Parts 2 & 3 you have to correct formula, use F=ma. Part 2 you should get the correct answer which should be greater than the static weight. I can't tell if part 3 is a trick question since I believe that would make your "tension force" in the other direction i.e. a compression force and a rope cant carry compression...
  4. Sep 17, 2010 #3
    brain fart..on part 3 since the acceleration is less than gravity you would still need a tension force up.
  5. Sep 20, 2010 #4
    thank you for the response!
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