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Homework Help: How far will an object travel on a flat surface

  1. Feb 25, 2009 #1
    Hi there,

    I am a physics idiot, but I still want to know where my object will end up ;)

    Here is what I am trying to do:

    I have a block that is sliding on a flat surface. I know the friction coefficient, the mass of the block, its initial position, gravity and initial velocity.

    How can I determine the distance the object will travel? I have been reading posts and articles on wikipedia, but I can't seem to get it right.

    distance = ?

    Any help is greatly appreciated.

  2. jcsd
  3. Feb 25, 2009 #2
    1. Set up a free body diagram showing the forces acting on the block once it's moving. You'll have its weight and the frictional force opposing motion (which you can find assuming Coulomb friction).

    2. Generate an expression that describes how the object will decelerate due to that frictional force if no driving force is acting upon it. Newton's second law will be helpful here.

    3. Assuming the frictional force is constant, the object's deceleration will be constant. Use a suitable form of the 1D kinematics equations for constant acceleration to express the distance to decelerate from the initial velocity to rest.

    4. Try and figure out where you've made assumptions that will cause your estimate to deviate from what you will see experimentally. There are probably quite a few!
    Last edited: Feb 25, 2009
  4. Feb 25, 2009 #3


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    Welcome to PF!

    Hi jtura ! Hi RODNEYpaul! Welcome to PF! :smile:

    To rephrase RODNEYpaul's advice …

    use the work-energy theorem …

    work done = energy lost …

    so on a horizontal surface, the only work done is friction times distance, and when that equals the original kinetic energy, the block has stopped. :smile:
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