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Basic Biomechanics

Basic Biomechanics. Mechanics-study of forces and motions produced by their action. Biomechanics-apply that to the structure and function of the human body. Basic Biomechanics. Statics deal with factors associated with nonmoving. Dynamics deal with moving systems

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Basic Biomechanics

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  1. Basic Biomechanics • Mechanics-study of forces and motions produced by their action. • Biomechanics-apply that to the structure and function of the human body.

  2. Basic Biomechanics • Statics deal with factors associated with nonmoving. • Dynamics deal with moving systems • Kinetics are the forces causing the motion • Kinematics are time, space and mass of the moving system.

  3. Basic Biomechanics • Kinematics- • Osteokinematics bones moving in space in regard to joint surface (flexion) • Arthrokinematics are the manner in which joint surfaces move in relation to each other.(concave)

  4. Basic Biomechanics • Vector- mechanical quantity having both magnitude and direction • Force is vector quantity-push or pull action • Force has direction and magnitude • You throw a ball with direction and speed

  5. Basic Biomechanics • Scalar- mechanical quantity that has only magnitude(strength of force). • Common scalar terms=Length, area, volume, mass • Mass is the amount of matter a body contains. • Inertia is change in motion in either speed or direction.

  6. Basic Biomechanics • Law of Inertia- an object at rest tends to stay at rest, and an object in motion tends to stay in motion.

  7. Basic Biomechanics • Think about what happens with your head in a car. It is not in motion, so when acceleration/deceleration happen your neck is not always happy.

  8. Basic Biomechanics • Law of Acceleration-the amount of acceleration depends on the strength of the force applied to an object.

  9. Basic Biomechanics • Acceleration is inversely proportional to the mass of an object. • If you roll a soccer ball , then a bowling ball, with the same force, the heavier object will not travel as far.

  10. Basic Biomechanics • Law of action-reaction- every action there is an equal and opposite reaction. • Strength of reaction is equal to strength of action, just in the opposite direction. • Harder you jump harder you rebound.

  11. Basic Biomechanics • Go outside and create a demonstration of one of the laws of physics for us all to understand. • In a simple paper write up what you have done and how it demo the law you chose. • You have 30 minutes to complete this task and paper.

  12. Basic Biomechanics • Force -a vector describes both magnitude and direction; push or pull; one object must act on another object For example a person pulling a box with a rope. The rope tension is the magnitude, the pull on rope is the direction.

  13. Basic Biomechanics • Force -a vector describes both magnitude and direction • Linear force- 2 forces act on the same line in the same direction or opposite direction. or

  14. Basic Biomechanics • Parallel Forces- • In the same plane and in the same or opposite directions.

  15. Basic Biomechanics • Concurrent Forces- two or more forces act from the same common point but pull in different directions. Resultant force will move toward stronger force.

  16. Basic Biomechanics • Concurrent Forces- two or more forces act from the same common point but pull in different directions

  17. Basic Biomechanics • Force Couple- two forces act in an equal but opposite direction resulting in a turning effect.

  18. Torque • Torque is the amount of force needed by a muscle contraction to cause rotary joint motion. • This is most effective at • 90 degrees • Read Torque(pg 97) • Fig 8-9, 8-10, 8-11

  19. Torque • Angle of Pull: angle between muscle insertion and bone on which it inserts. • Components of Force • Angular Force: force of a muscle contributing to bone's movement around a joint axis; greatest when muscles angle of pull is perpendicular to bone (i.e. 90 degrees). • Stabilizing force: degree of parallel forces generated on the lever (bone and joint) when the muscles angle of pull is less than 90 degrees. • Dislocating force: degree of parallel forces generated on the lever (bone and joint) when the muscle's angle of pull is greater than 90 degrees. force directed away from the joint (distal)

  20. Basic Biomechanics • State of equilibrium- when all torques acting on an object are even. • Center of gravity- COG-balance point of an object at which torque on all sides are equal. • In an adult the center of gravity is just anteior to s2

  21. Basic Biomechanics • Base of support is that part of the body that is in contact with the supporting surface. (BOS) • Line of gravity is the imaginary vertical line that passes through the COG to center of earth. (LOG) • Draw this in your notes pg 78

  22. Basic Biomechanics • Equilibriums • Sable- to disturb you would have to raise COG • Unstable- only slight force needed to disturb • Neutral- COG is not raise or lowered to disturb. • Lower COG is more stable.

  23. Basic Biomechanics • The closer COG is to center of BOS the more stable you will be

  24. Basic Biomechanics • Lets try it together. • Stand up and stand on both legs, then balance on one standing straight up. • Then lean to the side you are standing on. What changes. • Go do questions 7&8 in text pg 90 discuss

  25. Basic Biomechanics • List some ways to increase stability • Wider base of support • Greater mass (which will decrease speed) • Increase friction (carpet vs ice) • Focus on stationary

  26. Basic Biomechanics • Simple Machines • 4 types of Machines • Lever • Wheel and Axle • Inclined plane • The pulley

  27. Basic Biomechanics • Lever is a rigid bar that can rotate about a fixed point when a force is applied to overcome resistance.

  28. Basic Biomechanics • A-Axis is the fixed point around which the lever rotates. • F-Force causes the lever to move. (muscle in the body) • R-Resistance that must be overcome for motion to occur. ( can be gravity or the weight to move.)

  29. Basic Biomechanics Force Arm is distance between force and axis Resistance arm is distance from axis to resistance. A F R

  30. Basic Biomechanics • First-class lever FAR • Axis is located between the force and the resistance. • Balance R F A

  31. Basic Biomechanics • Second Class Lever ARF • Has the axis at one end, the resistance in the middle, and force at the other end. • power R F A

  32. Basic Biomechanics • Third class Leaver • Has the axis at one end with the force in the middle and resistance at the opposite end. • ROM R F A

  33. Basic Biomechanics • The body has more 3rd class levers because the body favors the advantage of ROM. • Levers can change class depending on where the resistance is, if there is resistance added vs just gravity. Or if the direction gravity comes from changes. Pg 83-84

  34. Basic Biomechanics • Mechanical Advantage- ratio between the force arm and resistance arm. MA=FA RA Less force is needed when mechanical advantage is greater. Page 85 force arm on leg

  35. Basic Biomechanics • Pulley is a grooved wheel that turns on axle with rope or cable. • It allows for change of direction of force or to change the magnitude of a force.

  36. Basic Biomechanics • Fixed pulley is one attached to a beam. It acts like a fist class lever, it is used to change directions. • Medical malleolus Acts as a pulley for the Tendon of peroneus longus

  37. Basic Biomechanics • Movable pulley has one end of the rope attached to a beam then the rope runs through the pulley to the other end where the force is applied. • What is gained in force is lost in distance.

  38. Basic Biomechanics • Wheel and Axle- a lever in disguise. • Wheel with a crank attached. It helps increase the force exerted. • Large radius requires less force.

  39. Basic Biomechanics • Incline Plane is a flat surface that slants. • It creates more distance with less effort

  40. Simple Machines • Basic rule of simple machines: what is gained in force is lost in distance. • Lever lab

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