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SX104

SX104. Week 8 Kinetics III Forces during walking, running and jumping Dr. Martine Deighan. Learning Outcomes. Explain the direction of the vertical velocity and acceleration of the CoM during the preparation for a vertical jump.

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SX104

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  1. SX104 Week 8 Kinetics III Forces during walking, running and jumping Dr. Martine Deighan

  2. Learning Outcomes • Explain the direction of the vertical velocity and acceleration of the CoM during the preparation for a vertical jump. • Know that Impulse = Change in Momentum and use this equation to calculate take-off velocity of a jump. • Be able to label diagrams of force vs. time during walking, running and jumping. • Know typical values of BWs for walking, running and jumping.

  3. Vertical Jump

  4. Start of Jump Accel = 0 Velocity = 0

  5. Accel Velocity Downwards Acceleration (speeding-up part of squat)

  6. Upwards Acceleration (slowing down to bottom of squat) Velocity Accel

  7. Velocity Accel Upwards Velocity

  8. Accel Velocity Take-Off(just before toes leave floor, accel becomes –ve as the body’s upward motion begins to slow down: accel = -9.81 m.s-1 once airborne)

  9. Force-Time Graph

  10. Vertical Jump Velocity

  11. Impulse = change in momentumUse this known relationship to calc. take-off velocity since v1 = start velocity = 0 and v2 = take off velocity Hence, take-off velocity is ______________by reducing the mass and increasing the Impulse (Ft). Impulse (Force x time) is the area under the force vs. time graph.

  12. Impulse on Force-Time Graph NOTE: the impulse is only considered from the start of the movement, until the end of the movement, i.e. take-off.

  13. Net Impulse -ve Area +ve Area -ve Area

  14. Landing Force in Vertical Jump

  15. Drive Flight Landing Mid-stance Forces in Stride Phases

  16. Forces in Walking Landing Drive Support Contact

  17. Forces in Jogging

  18. Forces in Sprinting Drive Contact Take-Off

  19. Walk vs Run

  20. Landing style in running

  21. Walk vs run: braking and propulsive forces

  22. Horizontal Impulse – how we can tell if someone is speeding up or slowing down Zero Acceleration Positive Horizontal Acceleration Negative Acceleration Negative impulse from landing phase Positive impulse from drive phase

  23. Walk vs run: mediolateral forces

  24. Reading • Hall, pg. 395 – 399. • Hamill and Knutzen, pg. 365 – 368 (the equations on these pages are not part of the learning outcomes for this lecture).

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