1. Mechanical Concepts

2. Basic terms and concepts Force - a push or pull has magnitude, direction, and point application Weight - gravitational force exerted on a body, measure on scale Torque – The turning force that tends to produce rotation around an axis (an off center force) T = Fd Moment arm – (d) the distance from axis where force is applied

3. Mechanical loads on the body Compression - Tension - Shear - Acute Loads - Repetitive -

4. Load/deformation curve or Stress/strain Deformation Plastic Region Ultimate Failure Point Yield Point Elastic Region Load

5. Mechanical loads What is stiffness of materials? stress/strain in a loaded material (slope on load/deformation curve; modulus of elasticity) What is strength? area under the curve

6. Acute vs repetitive loading Likelihood of Injury Frequency of Loading Load Magnitude

8. Levers Definition - a rigid ‘bar’ that rotates around an axis Contains resistance force, effort force, and axis (arrangement determines class of lever) In the body, bone is ‘bar’, joint is axis, muscle is typically effort force, segment weight + objects are resistance forces

9. First class levers

10. 2nd Class levers

11. 3rd class levers

12. Levers Depending on arrangement of components, levers can be used for force multiplier or speed and range of motion multiplier Mechanical advantage = EF moment arm/RF moment arm

13. Is MA improved?