Simulation of an Upper Limb I

Objectives:
  1. Apply the conditions of equilibrium to determine the amount of force that is exerted by the person’s deltoid Fdel when the person holds a ball with their arm horizontal.
  2. Calculate the magnitude and direction of the Joint Reaction Force on the shoulder (JRFs).
  3. Understand the mechanism by which the small weight of the ball can cause large magnitudes of Fdel and JRFs.

Teaching notes

Instructions:

In the following table, please input the height of the person, Hp, the weight of the person, Wp and the weight of the ball, Wbal. The simulation is calculated based on a normal proportional person. The weight of ball approximately acts on the hand, the end of the blue line. Once the input is set up, you can click “Calculate” button to obtain the values for each force and its lever arm.

Weight of the person WP= N.       Height of the person HP= m
      Θdel= 15˚
  Force   Lever arm
  Arm   WA= N.   LAA= m
  Ball   Wbal= N.   LAbal= m
  Deltoid   Fdel = N.   LAdel= m
  Component values   JRFsh=N.   JRFsv=N.
  JRFs=N.

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This work by Dan Liu and Matthew Burk is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.