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Homework Help: Pulling out a book (friction problem)

  1. Feb 26, 2010 #1
    Two books are lying on top of each other on a table. The upper book has a mass m1 , and
    the lower book has a mass m2 . The coefficient of static fric-
    tion between the books is µ1 . The coefficient of static friction
    between the book and the table is µ2 and the coefficient of
    dynamic friction between the book and the table is µd . You
    pull on the lower book with a horizontal force F .

    (a) How large must F be for you to start pulling both books
    along the table.

    (b) How large must F be for you to pull out only the lower

    (a) I reasoned that to get the books going at all we must have that [tex]F> \mu_s(m_1+m_2)g[/tex] and then once it is going we must ensure that [tex] \mu_1 m_1g > F > \mu_d(m_1+m_2)g[/tex]

    (b) To get the book going we must again have that [tex]F> \mu_s(m_1+m_2)g[/tex], but then once it is going [tex]F > \mu_d(m_1+m_2)g \wedge \mu_1 m_1g [/tex].

    Is this the correct reasoning here? We must split the problem up in two parts right?
  2. jcsd
  3. Feb 27, 2010 #2
    Noone who can help me with this?
  4. Feb 27, 2010 #3


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    Science Advisor
    Homework Helper
    Gold Member

    You seem to have a lot of extra stuff in your response. Part a asks for the value of F required to move the books. Please provide one answer only for the value of F in part a and correct any typos.

    For part b, again provide one answer and correct any typos. Whats that ^ in your equation??
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