Unformatted text preview: force in the erector spinae muscle. Assume that the head and torso weight 40 lbs. (2 inches in front of the spine) and the two arms weight 10 lbs. 2b. Next, consider that the child does not want to be picked up and is kicking his or her feet. The child’s center of mass moves back and forth as well as up and down according to a sinusoid (amplitude = 1 inch, frequency = 1 Hz). Write out the kinematics (position, velocity, and acceleration) of the system’s center of mass. (5 points). Write out the equations for the shear, compressive, and erector spinae forces. What are they? Will the peak magnitude of those forces increase or decrease compared to the static case? 3. Assume you are wearing a 25 lbs. backpack (all the other parameters are the same as the normal sized human from problem 1). What is the force on the vertebral body if the erector spinae muscles are the only ones providing stability....
View
Full
Document
This document was uploaded on 12/21/2011.
 Fall '09

Click to edit the document details