1 / 18

Equilibrium & Movement

Equilibrium & Movement. Today…. Review the concept of torque Discuss the concept of static equilibrium Define COG and discuss its significance Explain how mechanical factors affect a body’s stability. Torque. What is it? How do we define it? What is the moment arm?. Torque.

nowles
Download Presentation

Equilibrium & Movement

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Equilibrium & Movement

  2. Today… • Review the concept of torque • Discuss the concept of static equilibrium • Define COG and discuss its significance • Explain how mechanical factors affect a body’s stability

  3. Torque • What is it? • How do we define it? • What is the moment arm?

  4. Torque • What is the significance of moment arm length? • What are the three classes of levers? • What is mechanical advantage?

  5. Mechanical advantage • Ratio of the force arm to the resistance arm for a given lever M.A. = moment arm (force) moment arm (resistance) ** > 1 then force required is less thanthe magnitude of the resistance ** <1 then force required is greater but moves through a larger range

  6. Static equilibrium • “..a motionless state characterized by balanced forces..” • Sum of all vertical forces must be 0 • Sum of all horizontal forces must be 0 • Sum of all torques must be 0

  7. Static equilibrium How much force must be produced by the biceps brachii, attaching at 90° to the radius at 3cm from the center of rotation at the elbow joint, to support a weight of 70 N held in the hand at a distance of 30 cm from the elbow joint?  = (Fm)(dm) – (wt)(dwt) 70 N

  8. Static equilibrium The quadriceps tendon attaches to the tibia at a 30 angle 4 cm from the joint center at the knee. When an 80 N weight is attached to the ankle 28 cm from the knee joint, how much force is required of the quadriceps to maintain the leg in a horizontal position? 30° 80 N

  9. Center of Gravity • Center of mass: point at which the body’s mass is equally distributed in all directions • AKA center of gravity: point at which the body’s weight is equally balanced  = 0

  10. Locating the center of gravity • For a single segment object • For the body • Mechanically the body behaves as if all the mass is concentrated at the COG • Analysis tracks the path of the COG

  11. Locating the center of gravity • For multiple segment body • Movement of any segment changes weight distribution • Two methods for locating

  12. Locating the center of gravity • Segmental method • Based on mass and COM of individual segments • From film/video images

  13. Locating the center of gravity • Reaction board method

  14. Stability & Balance • Stability: resistance to disruption of equilibrium • To linear and angular acceleration • Examples of activities where stability is desirable??? • Examples of activities where minimal stability is desired?

  15. Stability & Balance • Balance: the ability to control equilibrium • Mechanical factors affecting – • Mass – Advantage? Disadvantage? • Friction

  16. Stability & Balance • Base of support • Relation to COG • Size • Horizontal location of COG • Vertical location of COG

  17. Tomorrow • Fluid mechanics

More Related