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Find the frictional force on the block

  1. Nov 13, 2015 #1
    1. The problem statement, all variables and given/known data

    When an 8.0 N force is exerted horizontally on a 10.0 kg block, the block’s acceleration across a level surface is 0.2 m/s2.

    a. Find the coefficient of kinetic friction between the block and the surface.

    b. Find the frictional force on the block.

    c. Find the net force.


    2. Relevant equations

    F=ma?
    Ff = mu x fN
    fk = muk x fN

    3. The attempt at a solution

    i can't find the kinetic mu so I'm not sure how to get any of it
     
  2. jcsd
  3. Nov 13, 2015 #2

    Doc Al

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    Try answering those three questions in reverse order. First: What's the net force on the block?
     
  4. Nov 13, 2015 #3

    SammyS

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    Hello katie beisel. Welcome to PF.

    In general, you need to show effort at solving/understanding the problem before we can help you.

    For your problem, it may not be best to answer the questions in order: a, b, c.

    Try answering any part you can.
     
  5. Nov 13, 2015 #4
    ok i got that f net is 2 N by using Fnet = ma and i have that the force normal is 98 N
     
  6. Nov 13, 2015 #5

    Doc Al

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    Excellent! Part C is done.

    Now work on B. Hint: Draw a free body diagram for the block.
     
  7. Nov 13, 2015 #6
    would the frictional force be 6 N because the force push is 8 N and the net force is 2 N so 8 - 2 = 6?
     
  8. Nov 13, 2015 #7

    Doc Al

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    Exactly right! B is done.

    Keep going.
     
  9. Nov 13, 2015 #8
    is the frictional force and the kinetic friction the same?
     
  10. Nov 13, 2015 #9

    Doc Al

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    Yes, since the block is sliding, the friction is kinetic friction.
     
  11. Nov 13, 2015 #10
    ok so then the coefficient of kinetic friction is .06 and with sig figs its .1
     
  12. Nov 13, 2015 #11

    Doc Al

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    .06 is already rounded to one sig fig. (Leading zeroes don't count.)

    But good! You solved it.

    Next time don't be shy about jumping in wherever you can. (And always show how you arrived at an answer.)
     
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