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Homework Help: Center of mass question

  1. Jan 23, 2010 #1
    A wire of uniform density is bent into the shape shown in the figure below.

    The value of L is 0.740 cm. Answer the following questions assuming that the origin is at the bottom left corner.

    What is the value of xcm?

    What is the value of ycm?

    xcm = 2*.74 = 1.48 cm

    ycm = .74 cm

    I get the feeling that this is wrong.

    Attached Files:

  2. jcsd
  3. Jan 23, 2010 #2


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    Gold Member

    First of all, treat this as 2 separate rods. Find the center of the vertical rod, and find a center of horizontal rod.

    Now redraw this problem as a 2 particle problem, where each particle is located at the center of each rod. For the vertical rod, the center is at (0,L/2), and for horizontal rod the center is at (2L/2,0). Now you have 2 particles and you can find a distance between them.

    I'll attach the picture but you are going to have to do all the calculations to get actual coordinates. Use it as a visual aid.

    Also I'm sure you wont be able to solve this without one more hint: think about the horizontal vs vertical rod. They are not of the same mass, hence the point particles are not of same mass.
    Last edited: Aug 21, 2010
  4. Jan 24, 2010 #3
    the answer i put for the first part was 0.493 and it was right. But for the secound part i got 0.493 as well is that right? i am not sure and really need an answer fast.
  5. Jan 24, 2010 #4


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    Post your work. Refer to my graph I already gave you the center of mass, for y its between 0.1 and 0.15.
  6. Jan 24, 2010 #5
    thanks for all your help! i just forgot to divide by two
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