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Frictional force problem

  1. Jul 25, 2012 #1
    1. The problem statement, all variables and given/known data

    a toy is dragged along a rough floor by a child

    (a) when the child applies a force of 0.50N horizontally the velocity is contant at 1.0 m/s. What is the force of friction on the toy?

    (b)when the child pulls harder so that the applied force is 1.00N the velocity of the toy increases uniformly to 2.0 m/s in 5.0 seconds. Calculate the acceleration of the block.

    (c) find the mass of the toy

    2. Relevant equations

    (a) Do I have to use the frictional force equation to find the answer? (Ffric = μ* F norm)

    (b) should I use the net force equation? Fnet=M*A


    3. The attempt at a solution

    (A)I was considering using the frictional force equation to solve the problem but I don´t have all the variables

    (B) Velocity v Time graph perhaps?

    thanks for the help (I´m a noob in physics)
     
  2. jcsd
  3. Jul 25, 2012 #2

    tiny-tim

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    welcome to pf!

    hi inzektor95! welcome to pf! :smile:
    nope!

    you can find the friction force either from the cause or from the result

    from the cause, you would need to know the mass and the coefficient of friction … you don't, so that's out!

    from the result, you know the acceleration is zero, so you should be able to find the force of friction from the information given :wink:

    for part (b), again you could find the acceleration either from the cause or from the result …

    ues the result … you know the initial velocity the final velocity and the time, so use one of the standard constant acceleration equations :wink:
     
  4. Jul 25, 2012 #3
    Thanks for the quick reply :)

    For A

    how can i find the force of friction using the information given? do i have to use a specific equation?

    acceleration = 0
    velocity = 1.0 m/s
    force = 0.50N

    For part B

    Vi (initial)= 1.0 m/s
    Vf (final)= 2.0 m/s
    T = 5.0 s
    A = ?

    so in other words, I should use this equation?
    Vf = Vi + at

    thank you very much tiny-tim! :D
     
  5. Jul 25, 2012 #4

    tiny-tim

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    hi inzektor95! :smile:
    if the acceleration is 0, what is the net force? :wink:
    yup! :biggrin:
     
  6. Jul 26, 2012 #5
    thank you very much tiny tim:smile:
     
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