60 thoughts on “Homework 27.A”

    1. Bending moment diagram requires you to calculate BM at each cross section along the length of the beam. So it is better to write your moment equation about a fixed point like A. Hope this helps.

    2. Hello Stefan,

      We sum the moments around either A or B to eliminate one of thee reaction forces and solve for the other one then by summing the forces in the y-direction we can solve for the other reaction force

    3. Bending moment diagram requires you to calculate BM at each cross section along the length of the beam. So it is better to write your moment equation about a fixed point like A. Hope this helps.

    1. Hello Lucas,

      Yes A is a pin joint, but since no horizontal forces are acting on the beam, thus it has only a vertical reaction force, so it seems like its acting like a roller support

    1. I believe you are correct that there is no moment at A because it is a pin joint; however, summing the forces in the x direction will only include Ax which must equal 0.

      1. Wei-ting is right in that there will always be a positive shear force and a positive moment on the place you cut. Just remember that the side that you make your cut will influence the direction of the shear and moment. For example, if you make your cut and have the right face exposed, the shear force will be positive downward.

  1. When making our V(x) and M(x) graphs, should keep them as open lines just on an xy plane or enclose the ends to the axies and shade in the area between the line and x-axis?

    1. Basically the moments occur at the ends of each segment which you can label as point P where the V force and Fn force are as well. It occurs at the ends where you cut off the segments. There shouldn't be a moment at Point E

    1. I believe when solving for your reaction forces, you use a moment about A in a global fbd so you're able to solve for the Dy reaction force. From there you can solve for the A reactions using sum of forces

    1. You don't know, so you designate that distance as x. Therefore, the shear force and bending moment will both be functions of x. Additionally, x should always be measured from the same point for all cuts. That is, if you wanted to move left to right, you would have different x's for each segment, but they would all be measured from point A (for instance, for the second segment between B and D, x would be measured from A on the left to some point between B and D on the right. Therefore, d <= x <= 2d).

    1. You should have one for each segment in which the shear force and bending moment is different. So one for when 0 <=x<=d, a
      second one for d <= x <= 2d, and a third one for 2d <= x <= 3d.

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