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Homework Help: Introductory Physics question in Forces and Works chap.

  1. Dec 7, 2015 #1
    First of all, I am not from English-using country so excuse my short english skill.

    This is the question from Halliday. I have solved this problem and checked the answer from my reference
    which started its statement with below

    F + Fn − (m + M)g = (m + M)a
    where m = 0.250 kg is the mass of the cheese, M = 900 kg is the mass of the elevator cab,
    F is the force from the cable, and 3.00 N, Fn = is the normal force on the cheese.

    And I think this explanation is wrong
    Shouldn't it be F - (m+M)g = (m+M)a ?
    Cuz what I think is
    for elevator) F-Mg-Fn=Ma (i)
    for cheese ) Fn-mg=ma (ii)
    (i)+(ii) -> F - (m+M)g = (m+M)a

    If I am wrong, please tell me what is my error.
  2. jcsd
  3. Dec 7, 2015 #2
    You're right and your reference is wrong.

  4. Dec 7, 2015 #3
    Thank you for your help!
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