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Homework Help: Free body diagram problem assistance

  1. Mar 11, 2012 #1

    I'm having a bit of trouble with a Free Body Diagram question and I'm not sure if I'm going about it properly.

    The question asks;

    A 82kg couch is being pushed with a force of 56N at an angle of 40 degrees above the horizontal. If the coefficient of friction between the couch and the floor is 0.051, what is the acceleration of the couch?

    My final answer was it accelerated at 0.02m/s^2.

    I think I am incorrect because the acceleration in the vertical has to be 0, and therefore Fg, Fn and Fappv must balance out to 0. If so, I will have a different Fn. Can someone let me know if I'm on to something?
  2. jcsd
  3. Mar 11, 2012 #2
    Please don't give me the answer for the problem as I want to figure it out myself. But right now I'm confused assuming that if there's acceleration on the horizontal, that it is also on the vertical? For some reason I think a=0 on the vertical, but I'm new.
  4. Mar 11, 2012 #3
    Imagine pushing a couch at an angle with a moderate force. Is the couch either going to "fly" upwards or fall through the floor? If you believe it's no to both of these possibilities then the acceleration on the vertical must be zero. Often times when you're confused with physical situations it's helpful to imagine them out and the implications of different values...

    if you could show the resultant forces you've found for horizontal and vertical and how you found them, I may be able to help you find your mistake.

    btw you've posted your question in the wrong section. this is for pre-cal math questions.
    Last edited: Mar 11, 2012
  5. Mar 11, 2012 #4
    Thanks for your help, I think I was able to figure it out.
    The only acceleration would be on the x-axis in the direction the couch is moving, therefore Fnet in the y-axis would be 0 and my normal force, force of gravity, and applied force (y-axis) should = 0. Therefore the normal force would be the difference of the force of gravity and force applied (y axis). And i think everything just falls into place after that.

    What do you think?
  6. Mar 11, 2012 #5
    Sorry for posting in the wrong area....new to all of this.
  7. Mar 12, 2012 #6
    Sounds perfect :smile:
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