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Help! Weight components

  1. Nov 6, 2009 #1
    1. The problem statement, all variables and given/known data
    A simple one mark question which is doing my head in.
    'There is a lorry travelling up a slope. Angle of slope is 46 degress with the horizontal and the weight of the lorry is 240000N. A resistive force of 1200N down the slope acts on the lorry as it travels up the slope at a constant speed of 15 meters per second.
    Q: Show that the component of the weight down the slope is 20000N

    2. Relevant equations



    3. The attempt at a solution
    I simply can't get my head round it. Why would the weight change? Wouldn't weight remain constant whatever the lorry is doing?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Nov 6, 2009 #2
    You are right the weight doesnot change.But it has 2 componets.One opossite to the direction of the movement of the lorry an one vertical to the slope.
    So by the pythagoras theorem root(Wx^2 + Wy^2)=W
    where Wx is the the componet of the weihgt parallel to the slope and Wy the one vertical to the slope
     
  4. Nov 6, 2009 #3
    Take a look of what i mean.
     

    Attached Files:

  5. Nov 6, 2009 #4
    I am sorry i probably misunderstood your question
     
  6. Nov 6, 2009 #5
    Did you cinsider the case tha the question is wrong.The weight cannot change.Wx=240000*sin46
     
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