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Equations of motion for uniform acceleration

  1. Mar 11, 2007 #1
    1. The problem statement, all variables and given/known data

    Hi All,

    The question That I am stuck on is:

    A packing crate has a nass 100kg is allowed to slide down on a ramp until it hit the ground. The friction resistance to motion is 240N. The length of the ramp is 10 m and thehieght of the crate from the ground just before it started to slide is 6m. Calculate the speed of the crate just before it hits the ground

    To be perfectly honest, I don't know where to start!! What would you work out first, don't want the answer just help on how to tackle the question - what needs to be worked out first?

    2. Relevant equations

    g= 10N/Kg

    I've found these equations while researching (I think they are relevant):

    Speed = Distance / Time

    Velocity = speed + Direction

    Work = Force x Distance

    3. The attempt at a solution

    Don't know where to start:surprised

    Any advice would be most welcome
  2. jcsd
  3. Mar 11, 2007 #2


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    Gold Member

    The first thing i would do with a question like this is draw a diagram and clearly label it, including all of the forces that are present
  4. Mar 11, 2007 #3
    Cheers Dango

    I Have a diagram, but dont know what or how to tackle the question?

    Dont know how gravity / crate weight vs friction is worked out with an incline plane?

    Would like some advice, direction as what to calculate first - I aint got a clue, have searched wikipedia etc and still don't understand stand:cry:
  5. Mar 11, 2007 #4
    A problem like this is probable easier in terms of energy conservation
  6. Mar 11, 2007 #5


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    Gold Member

    Do you know how to resolve a force into its horizontal and vertical parts ?

    You also need this formula

    acceleration = force/mass
  7. Mar 11, 2007 #6
    I think it's way easier if you use work formula:
    change in energy = force applied in that direction x distance

    ignore everything else, and find the net force in the direction that object is moving
    and only energy changing i kinetic energy
  8. Mar 12, 2007 #7
    Work done by Friction + Work done by gravity = Final K.E. - Initial K.E.

    <i hope this is right!!>
    now, u can work out the individual work done and find v.
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