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Homework Help: Quick questions

  1. Sep 25, 2009 #1
    1. The problem statement, all variables and given/known data

    A mass M is initially at rest on a horizontal surface, mus=0.30 and muk=0.20 . A horizontal string then pulls M with a tension T. Forces below are magnitudes

    A) N equals Mg
    B) If M does not accelerate, then T less than or equal mu_s N
    C) M will accelerate if T exceed mu_s N
    D) M will accelerate if T exceeds mu_k N
    E) T equals mu_s N if M remains at rest
    F) The NET force on M (if M does not move) is T

    3. The attempt at a solution

    Ok so im not sure which Im getting wrong here. Im supposed to choose which ones of them are right but I cant get it. If someone can tell me where im messing up.

    Im putting
    for correct.
  2. jcsd
  3. Sep 26, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    How hard do you have to pull to start M moving (and thus accelerating)? Remember that it starts from rest.

    If you pull and it doesn't move, what can you say about the friction force? How does that friction force compare to the maximum static friction force?

    (Two of your answers are wrong.)
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