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A 10.0-kg mass is placed on a 25.0o degree incline and friction keeps it from sliding

  1. Nov 5, 2012 #1
    1. The problem statement, all variables and given/known data

    A 10.0-kg mass is placed on a 25.0o degree incline and friction keeps it from sliding. The
    coefficient of static friction in this case is 0.580, and the coefficient of sliding friction is
    0.520. The mass is given a shove causing it to slide down the incline.

    2. Relevant equations

    What is the frictional
    force while the mass is sliding?

    3. The attempt at a solution

    This is all I have so far, but I don't exactly understand it:

    Frictional force while the mass is sliding = μmgcosθ = 0.52 X 10 X 9.8 X cos 25
    = 46.19 N


    I need a full step-by-step explanation, if possible. I'll also take any other information about the problem that may make it easier. Thank you.
     
  2. jcsd
  3. Nov 5, 2012 #2

    Delphi51

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    Re: A 10.0-kg mass is placed on a 25.0o degree incline and friction keeps it from sli

    Your 46.19 is correct.
    You also need to find the downward, along the ramp force. It is the other component of mg, that is mg*sin(25). The net force along the ramp is this force minus the friction force.

    I always draw the ramp, put the mass at the very top and draw the mg force vector straight down. Then separate that mg into the sum of a force along the ramp and perpendicular to the ramp. The perpendicular force is the normal force pulling the mass against the ramp surface.
     
  4. Nov 5, 2012 #3

    Simon Bridge

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    Re: A 10.0-kg mass is placed on a 25.0o degree incline and friction keeps it from sli

    Welcome to PF;
    Draw a free-body diagram for the mass and you'll see how that relation was found.
     
  5. Nov 5, 2012 #4
    Re: A 10.0-kg mass is placed on a 25.0o degree incline and friction keeps it from sli

    I'll do all of the above. Thank you.
     
  6. Nov 7, 2012 #5

    Simon Bridge

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    Re: A 10.0-kg mass is placed on a 25.0o degree incline and friction keeps it from sli

    Cool! Let us know how you get on.
     
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