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Homework Help: Ok, this picture is a bit harder to understand.

  1. Sep 25, 2005 #1
    Hi again :biggrin: ,

    here's another one of my find picture questions. In the following picture I had a guy on one hand. Now, it says the ground reaction force is 1000 N and I have to resolve this force into it's vertical and horizontal components.

    One hand position

    My questions are:

    1)The ground reaction force is just straight up correct? It is also equivalent to the one going straight down. F=mg. So that would be the vertical component...

    2)This is the confusing part? How could I resolve into horz and vert if that's already the vertical? On the picture I drew what I think is correct but...

    3)I can't find a way to solve for these components with only one piece of info??? Unless I don't have to...it asks to resolve into components, does that mean I have to solve as well?

    4)Oh, and last question about center of mass...is it true that if I drew straight lines from each say fot and hands, that the convergent point is usu where the center of mass lies? :yuck: :yuck:

    Any help appreciated!!
  2. jcsd
  3. Sep 25, 2005 #2
    1) The ground reaction is opposite to the diagonal arrow, almost in line with the left arm of the man. There must be a horizontal reaction of the ground for the to be able to stand on his hand as is shown on the picture. This horizontal component equals the cofficient of friction between the floor and the hand multiply by the weight of the man.
    The vertical component of the reaction of the floor equals the weight of the man

    If you do not know the coefficient of friction between the hand and the floor, measure on the picture the angle between the harm and the vertical, and using trigonometry you wil be able to determine the horizontal component of the reaction of the floor and than calculate the diagonal force with Pythagoras theorem.

    There is an other way.
    Measure directly on the picture with a ruler the vertical arrow and scale the 1000 N force along this arrow, trace a horizontal line at the end of the arrow to make a right triangle with the hypotenuse traced alog the arm. The measure the length of the hypotenuse, then you will be able to calculate the reaction of the floor.
  4. Sep 25, 2005 #3
    Yeah, my teacher for some reason doesn't want to use trig and goes by the measure and scale method lol, so much more tedious. Thanks for the help!

    oh yea, what about the way I found the center of mass, is there any logic behind that?
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