Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Biomechanics HW Problem

  1. Nov 2, 2006 #1


    User Avatar

    I have a Force Acceleration analysis that I am un sure of. I have a picture of a skull that is punched/kicked/whatever in the chin.

    Problem Statement:

    The head shown in the figure below is considered a rigid body. IT rocks on the occipital condyle, C, where an axial force, Fa, and a shear force, V, and a neck torque, To, resist the motion. A blow is applied to the chin at point B at an angle of 63 degrees relative to the horizontal. The initial linear acceleration, a, of the mass center, G, is photographically deteremined to be 140 x gravity. For a head of mass 3.5kg, a moment of inertia of 0.0356 kgm^2 about an axis perpendicular to the sagittal plane is calculate.d WHat are the reactions at the occipital condyles if torque To is neglected?

    Ive used the parallel axis theorem to find my actual needed inertia.

    I am thinking that maybe I need to do a sum of moments about the condyle to find a reaction force, but I'm not sure if that is right or how to do it. I can't figure out how to incoroporate the moment of inertia.

    If anyone can help shed some light for me, I would appreciate it.

    I will also be around to answer any questions one might have.

    Thanks a bunch.
  2. jcsd
  3. Nov 2, 2006 #2


    User Avatar

    After doing some research, I have come to the conclusion that if i neglect torque, then I don't even need to worry about moment of inertia. Is this correct? I can't find any equation that relates linear motion with moment of inertia unless there is torque involved.

    Is this correct?
  4. Nov 2, 2006 #3


    User Avatar
    Homework Helper

    You may want to put an image on the web, since I don't see any included in your post. Until then, no one will probably be able to help you. :smile:
  5. Nov 2, 2006 #4


    User Avatar

    Here is an attachment of what my assignment is.

    Attached Files:

    Last edited: Nov 2, 2006
  6. Nov 2, 2006 #5


    User Avatar

    The answer I came up with is about 9500 N. Is this possible?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook