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Homework Help: Kinetic Friction Problem [FORCES]

  1. Oct 23, 2013 #1
    1. The problem statement, all variables and given/known data

    A block is pushed across a horizontal surface with a coefficient of kinetic friction of 0.15 by applying a 150 N horizontal force. The block accelerates at 2.53 m/s^2. Find the mass of the block.

    2. Relevant equations

    ƩF = ma

    3. The attempt at a solution

    μk = 0.15
    Fa (applied force) = 150 N
    a = 2.53 m/s^2
    m = ?

    I understand I must find the frictional force first, correct?
    and Ff (frictional force) = μFN (normal force)

    And to find normal force, FN = mg
    but then I come across this, which also requires for me to find mass...?
    What can I do?
  2. jcsd
  3. Oct 23, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper

    No, you don't need to find the mass first. Just leave Ff=μmg. The total force is F is Fa-Ff. Since F=ma, Fa-Ff=ma. Put it all together and you should be able to solve for m in the end.
  4. Oct 23, 2013 #3
    Ohh ok, so I did Fa - Ff + Ff = ma + μmg
    and I got the correct mass. Thank you so much!
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