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Forces, elevator, acceleration -- I have the answer, just please help explain it...

  1. Oct 20, 2015 #1
    1. The problem statement, all variables and given/known data
    When a 45-kg person steps on a scale in an elevator, the scale reads a steady 480 N. Which of the following statements must be true? There could be more than one correct choice.
    a) The elevator is accelerating upward at a constant rate
    b) The elevator is moving downward at a constant rate
    c) The elevator is moving upward at a constant rate
    d) The elevator is accelerating downward at a constant rate
    e) From the given information, we cannot tell if the elevator is moving up or down

    2. Relevant equations
    F = ma
    Fg = mg
    3. The attempt at a solution
    From the equation, I know that the Fg is (45)(9.8) = 441.
    I think the answer is a. But my textbook says that it is both A and E. Can someone help explain why? Thanks in advance :)
     
  2. jcsd
  3. Oct 20, 2015 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Hint: "moving up or down" refers to velocity, not acceleration. What's the difference?
     
  4. Oct 20, 2015 #3
    oh ok gotcha thank you :)
     
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