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- 2. Overview Debunking the Myth The Righting Reflex Drag and Air Resistance Angular Momentum
- 3. Debunking the Myth It has long been speculated that a cat will always fall on its
- 4. Debunking the Myth But how does the cat do this? Does it know how to push
- 5. Debunking the Myth Étienne Jules Marey (1830-1904) Marey was a French doctor, and one of the
- 6. Debunking the Myth In 1894, in response to a call for information from the Academy of
- 7. The Righting Reflex The righting reflex is innate in cats, and develops between the ages of
- 8. The Righting Reflex Cats depend largely on visual cues to right themselves. Their vestibular system also
- 9. Drag and Air Resistance In 1553, Giambattista Benedetti (1530-1590) determined that all objects fall with the
- 10. Drag and Air Resistance But this is not the whole story! A falling object is slowed
- 11. Drag and Air Resistance The force due to air resistance is given by: where, Cd =
- 12. Drag and Air Resistance Since the air resistance acts upwards, it tries to slow down the
- 13. Drag and Air Resistance Terminal velocity: v ~ 614 mph (maximum speed of skydiver) v ~
- 14. Drag and Air Resistance A skydiver’s parachute has a much larger area than the diver himself,
- 15. Drag and Air Resistance A cat can change its terminal velocity by spreading out its limbs
- 16. Angular Momentum A cat can determine which way is up, and has a slow enough terminal
- 17. Angular Momentum Angular momentum is a quantitative measure of how much an object is rotating. The
- 18. Angular Momentum One of the most basic laws of physics is the conservation of angular momentum:
- 19. Angular Momentum Skaters use this conservation of angular momentum to speed up their spins: large r,
- 20. Angular Momentum The only outside forces acting on the cat are gravity and air resistance. These
- 21. Angular Momentum The cat could potentially use air resistance to change its rotation and turn itself
- 22. Angular Momentum The answer: the cat’s entire body cannot rotate at once.... ...But cats are very
- 23. Angular Momentum A cat begins by spreading its hind legs very wide, and pulling in its
- 24. Angular Momentum Let’s look at the cat’s angular momentum: front half – v is large and
- 25. Angular Momentum
- 26. Angular Momentum The front and the back of the cat have angular momentum in opposite directions,
- 27. Angular Momentum The cat then reverses the process: it spreads its front legs and pulls in
- 28. Angular Momentum The result: the cat turns over to land on its feet, but its total
- 29. How a Cat Lands on Its Feet
- 30. How a Cat Lands on Its Feet A study was released in the Journal of the
- 31. How a Cat Lands on Its Feet Above a fall height of 7 stories (around 70
- 32. How a Cat Lands on Its Feet Summary: sequence of events cat determines which way is
- 33. DO NOT TRY THIS AT HOME Although a falling cat has a very good chance of
- 34. Further Questions What triggers the “righting reflex” to kick in? Can a cat reorient itself with
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