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Homework Help: Calculate the Support Reactions at A and B as a Result of the Force

  1. Nov 10, 2012 #1
    1. The problem statement, all variables and given/known data
    The load per foot of beam length varies as shown. For x = 17 ft, the unit load is 373 lb/ft. At x = 0, the load is increasing at the rate of 41 lb/ft per foot. Calculate the support reactions at A and B. The reactions are positive if upward, negative if downward.

    I have attached an image of the question.
    2. Relevant equations

    3. The attempt at a solution
    I know that I need to integrate the function, w = k1x - k2x2 but I'm not sure how to find the variable k1 and k2. Plugging in the information that when x = 17, w = 373 I get

    373 = 17k1 - 289k2

    But I'm not sure how to proceed from here. I realize that it also says that when x = 0 the load is increasing at a rate of 41 lb/ft but I'm not certain how I should interpret this.

    Help would be appreciated. Thank you

    Attached Files:

  2. jcsd
  3. Nov 10, 2012 #2


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    Homework Helper
    Gold Member

    From the equation, when x=0, w=0. And you are given the slope at (0,0). So you have 2 points and a slope at one of those points. I think that is sufficient to find the constants k1 and k2.
    Last edited: Nov 10, 2012
  4. Nov 10, 2012 #3
    Oh, I've got it now. I just take the derivative of the function, then I can solve for k1 and k2.

    Thank you.
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