1. Psyc 552 Ergonomics & Biomechanics Lecture 8

2. Why Biomechanics?  1…  2…  3…

3. 3 Purposes  Advance “academic” knowledge  They evaluate real situations…  May be only method of assessing

4. Model Types  Static 2D…  Static 3D – Whole body models  Dynamic models

5. Single – Body Segment Static Model  Goal: Determine forces associated with a single body part. Rotational moments Reactive forces  To solve the problem we must: 1. determine the magnitude of the external force acting on the stationary mass.

7. Measurement  Gravity creates the weight of the mass  Weight is proportional to mass Weight = Mg  Weight is measured in Newtons M = mass in kg g = gravity 9.9 m/s 2

8. Measurement (cont)  The weight of a 15 kg object would be…  Forces are vector quantities and depict…

9. Static Equilibrium  If the load is not moving…  When upward lift = weight vector we have static equilibrium…  The hands must create an equal reactive force in the opposite direction.

10. Rotational Forces

11. Moments  The tendency to rotate The product of a force and the perpendicular distance from its line of action to the point of rotation.

12. Non-horizontal segments