Given the mass, angle, and the coefficient of static friction, find the pulling force

  1. 1. The problem statement, all variables and given/known data

    A father gives his daughter a ride on a sled by applying a force F at an angle θ = 26.0° with respect to the horizontal. If the coefficient of static friction is µs = 0.153, and the combined mass of sled and child is m = 24.0 kg
    What is the minimum amount of force required to move the sled from rest by
    pulling it

    2. Relevant equations

    F=ma

    3. The attempt at a solution

    I have tried multiple ways and i keep getting the wrong answer,
    I think i should take the sum of all the forces in the x direction and of the y direction and somehow get the force i need but im not exactly sure.

    HELP PLEASE?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Re: Given the mass, angle, and the coefficient of static friction, find the pulling f

    The words "minimum amount of force" and "from rest" imply that this is a statics problem. In statics, what is the special condition on the net force? What does the word "static" imply about the value of the acceleration in f=ma?
    Once you figure that out, you should have your net x force components (which requires trig) sum to this special value for the net force as well as you net y force components (which also requires trig).
    EDIT: Also make sure you have your pulling force in the correct direction. Did you draw a free body diagram?
     
  4. Re: Given the mass, angle, and the coefficient of static friction, find the pulling f

    So "static" would imply that the value of acceleration =0 ?right?

    so i have in the x direction:
    F(pull,x) + F(friction,x) +W(x) + n(x) = 0
    but there is no W or F(gravity) in the x direction so that equals zero and same for n(x) (normal force) =0.
    therefore i have:
    F(pull,x) +f(friction,x)=0 right?

    In the y direction:
    F(pull,y) + F(friction,y) +W(y) + n(y) = 0
    F(friction,y)=0
    therefore i have:
    F(pull,y) +W(y) + n(y) = 0 right?

    then F(pull,x) = F(pull)cosθ
    and F(pull,y) =F(pull)sinθ

    I all that ive said is correct now, what would i do now? or is there other things that i am missing ?
     
  5. Re: Given the mass, angle, and the coefficient of static friction, find the pulling f

    Since the force is pulling, is your pulling force positive or negative? Is your weight positive or negative?
    I see two equations and two unknowns (Fpull and normal). Pull out your algebra toolkit and solve it.
     
  6. Re: Given the mass, angle, and the coefficient of static friction, find the pulling f

    thanks for your help, i got the answer :P
     
Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook

Have something to add?