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BIOMECHANICS

BIOMECHANICS. April 24 2003. What is BIOMECHANICS?. BIO – the study of living materials MECHANICS - describing force, motion, and strength of materials. Biomechanics …….

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BIOMECHANICS

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  1. BIOMECHANICS April 24 2003

  2. What is BIOMECHANICS? • BIO – the study of living materials • MECHANICS - describing force, motion, and strength of materials

  3. Biomechanics …….. ….allows us to understand the human bodies normal function, predict changes due to alterations, and propose methods of artificial intervention. (Y.C. Fung).

  4. Biomechanics …….. • Biomechanics is a science that investigates motion and the effects of both internal and external forces that occur during the actions performed by living organisms. (John A. Mercer)

  5. Problems studied by Biomechanists • Why do some individuals slice a golf ball? • Why do some people use orthotics to relieve lower back pain? • What cues can a teacher provide to help students learn the underhand volleyball serve? • Why do some individuals experience knee pain?

  6. Problems studied by Biomechanists • Why do certain bicycle tires allow a rider to go faster? • What is the safest way to lift heavy objects? • NASA studies the effects of microgravity on the human musculoskeletal system.

  7. Why Study Biomechanics? • Biomechanical principles are applied by scientists and professionals in a number of fields to address problems related to human health and performance.

  8. Why Study Biomechanics? • Biomechanics is essential for the competent physical education teacher, physical therapist, personal trainer, coach, or recreation leader.

  9. How do we Analyze Human Movement? 2 ways to analyze human movement: 1) Qualitative 2) Quantitative

  10. Qualitative • Non numeric • description of quality • Good Poor • Long Heavy • Flexed Rotated MOTOR LEARNING INFO!!!!

  11. Quantitative • The use of numbers Six meters Three seconds Fifty turns Two players Ten dollars

  12. OUR GOAL • Biomechanists rely heavily on qualitative and quantitative techniques in attempting to answer specific questions. We are going to look at the quantitative aspect.

  13. Biomechanics Terms • To fully understand biomechanical problems we must first be familiar with biomechanics terms

  14. MASS (m) • quantity of matter contained in an object • measured in Kilograms (Kg)

  15. Velocity (v) • change in position with respect to time • Velocity = change in distance / change in time • v = d/t • measured in Meters per Second (m/s)

  16. Acceleration (a) • the rate of change in velocity • acceleration = change in velocity/ change in time • a = v2 – v1 / t • measured in Meters per Second Second (m/s/s) or (m/s2)

  17. Force (f) • a push or pull acting on a body • characterized by its magnitude, direction, and point of application to a given body • f = m x a • measured in Newtons (N)

  18. Vector • quantity that possesses both magnitude and direction

  19. 10 N east 5 N east

  20. Free body diagrams • sketch that shows a defined system in isolation with all of the force vectors acting on the system

  21. Newtons Laws

  22. Newton’s First Law • An object in motion will tend to stay in motion, and an object at rest tends to stay at rest, unless the object is acted upon by an outside force.

  23. HUH ?!?!?!?! • This means that if you leave a book on your coffee table over night, when you return in the morning, unless an outside force moved it, it will be in the same place

  24. OR • if you kick a soccer ball, it will continue moving until it hits something. However we all know the ball will eventually stop even if it does not hit a wall -- this is because of the friction between the ball and the ground, and between the ball and the air.

  25. Gimme a better example • One of the most common places people feel the First Law is in a fast moving vehicle, such as a car or a bus, that comes to a stop. An outside force stops the vehicle, but the passengers, who have been moving at a high speed, are not stopped and continue to move at the same speed.

  26. The crash dummy is not wearing a seat belt and is moving along with the car. Both the car and the dummy are moving at, say, 60 mph.

  27. When the car hits the cement road divider it is stopped (an outside force stops it from moving). The crash dummy, however, is not so lucky. Since he is not wearing a seat belt, and is not connected to the car, he will continue to move at 60 mph. This means he will go flying out through the front windshield

  28. please do not try this at home

  29. The dummy will fly through the air until he hits the ground. This is because the earth's gravity stopped him from moving any further (his trajectory is a combination of the downward force of gravity, and the horizontal force of the moving car).

  30. Newton’s Second Law • A force applied to a body causes an acceleration of that body of a magnitude proportional to the force, in the direction of the force, and inversely proportional to the body’s mass.

  31. HUH ?!?!?!?!?! • acceleration is produced when a force acts on a mass • If you push a ball, the ball will roll.

  32. AHHH????? • The bigger the ball the harder you have to push it. • ACCELERATION = MASS FORCE

  33. I need an Example • Kritz’s car, which weighs 1,000 kg, is out of gas. Kritz is trying to push the car to a gas station, and he makes the car go 0.05 m/s/s.

  34. How much force is required? FORCE = MASS x ACCELERATION

  35. FORCE = 1000kg x 0.05m/s/s FORCE = 50 N

  36. Jankura's van, which weighs 2,000 kg, is out of gas. Jankura is trying to push the car to a gas station, and he makes the van go 0.05 m/s/s

  37. How much force is required? FORCE = MASS x ACCELERATION

  38. FORCE = 2000kg x 0.05m/s/s FORCE = 100 N

  39. Newton’s Third Law • When one body exerts a force on a second, the second body exerts a reaction force that is equal in magnitude and opposite in direction on the first body.

  40. HUH?!?!?!?!?! • Every action has an equal and opposite reaction

  41. Want an example? • When you punch someone in the face, your hand not only applies a force to the person's face; the person's face applies a force to your hand. Since the person's face is softer than your hand it suffers more from the interaction.

  42. Of course there is a picture

  43. How does this rocket fly through space with no air for propellers to churn or jets to suck?

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