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How Can a Gecko Walk on a Ceiling?1 © 2009 McREL Physical Science Lesson 8 How Can a Gecko Walk on a Ceiling? Investigating Static Forces in Nature: The.

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Presentation on theme: "How Can a Gecko Walk on a Ceiling?1 © 2009 McREL Physical Science Lesson 8 How Can a Gecko Walk on a Ceiling? Investigating Static Forces in Nature: The."— Presentation transcript:

1 How Can a Gecko Walk on a Ceiling?1 © 2009 McREL Physical Science Lesson 8 How Can a Gecko Walk on a Ceiling? Investigating Static Forces in Nature: The Mystery of the Gecko

2 How Can a Gecko Walk on a Ceiling?2 © 2009 McREL Closer Look Image 8.3 Spatula-Shaped Tips Image 8.2 One Gecko Seta

3 How Can a Gecko Walk on a Ceiling?3 © 2009 McREL Tape and Spatula (d) 1m Spatula-shaped tips on gecko seta interacting with a smooth surface Transparent Tape on Glass Image 7.4 Image 8.6 Tape or Spatulas Hard Surface If one or both surfaces are compliant : Image 8.5

4 How Can a Gecko Walk on a Ceiling?4 © 2009 McREL What Is Happening Between The Surfaces? Play the “Hot Spots” Game to find out! http://dawn.jpl.nasa.gov/mission/ion_engine_interacti ve/lev2/index.html Or Charge Simulator: http://dawn.jpl.nasa.gov/mission/ion_engine_interacti ve/lev1/index.html http://dawn.jpl.nasa.gov/mission/ion_engine_interacti ve/lev1/index.html How does the kind of charge on the particle affect the deflection of the positively charged particle?

5 How Can a Gecko Walk on a Ceiling?5 © 2009 McREL What Did You Find Out From “Hot Spots?” 1. What is the effect of placing a negatively charged player (red dot) close to the path of the positively charged soccer ball (blue dot)? 2. What is the effect of placing a positively charged player (red dot) close to the path of the positively charged soccer ball (blue dot)? 3. What are your thoughts about the gecko seta surface and the ceiling surface as they relate to charges?

6 How Can a Gecko Walk on a Ceiling?6 © 2009 McREL Type of Interaction

7 How Can a Gecko Walk on a Ceiling?7 © 2009 McREL Questions 4. What makes you think that these attractions are weak? 5. Are these permanent or temporary attractions? How long do they last?

8 How Can a Gecko Walk on a Ceiling?8 © 2009 McREL + + - + + + + + + - - - - - - - + + - + + + + + + - - - - - - - Image 8.8Image 8.9 Describe the Interaction

9 How Can a Gecko Walk on a Ceiling?9 © 2009 McREL + + - + + + + + + - - - - - - - + + - + + + + + + - - - - - - - Image 8.10Image 8.11 Describe the Interaction

10 How Can a Gecko Walk on a Ceiling?10 © 2009 McREL Weak/Temporary Interaction Between Two Surfaces Image 8.14 – + Image 8.15 Image 8.13 Image 8.12 Single Gecko Seta Probe Surface

11 How Can a Gecko Walk on a Ceiling?11 © 2009 McREL Animation

12 How Can a Gecko Walk on a Ceiling?12 © 2009 McREL Animation

13 How Can a Gecko Walk on a Ceiling?13 © 2009 McREL Docking Animation Questions Which molecule has the most contact with the green molecule? Explain how shape affects the number of attractions between the object and the surface. Which molecule acts most like the gecko seta?

14 How Can a Gecko Walk on a Ceiling?14 © 2009 McREL Describe the number and size of forces involved in gecko adhesion. What part of the atom moves in response to momentary charge rearrangements? Describe this interaction between the electrons of each atom. Describe the overall charge and how long the attraction lasts. What Is Your Answer?

15 How Can a Gecko Walk on a Ceiling?15 © 2009 McREL Research Summary View the Nano in Nature video: http://www7.nationalgeographic.com/ngm/0606/feature4/ multimedia.html Adhesion force consistent with electric forces Adhesion enhanced by sliding, regardless of speed Adhesion force mainly independent of humidity Adhesion effective underwater Geckos walk through dirt—it normally takes about 5 steps for a gecko to recover adhesive capability after walking through graphite lubricant.

16 How Can a Gecko Walk on a Ceiling?16 © 2009 McREL Flow Chart 7.How Do We Measure Forces at the Nano Level? Scale: Visible and Invisible Dominant Force: Extremely Small, Large in Number Tools: Atomic Force Microscope 8. How Can a Gecko Walk on a Ceiling? Scale: Visible and Invisible Dominant Force: Electric Forces Tools: Atomic Force Microscope 6. How MUCH Force Is Needed to Make an Object Stick? What Factors Affect the AMOUNT of Force Acting? Scale: Visible Force: Gravity, Adhesive Tools: Spring Scale 2. What Do We Mean When We Speak About Surfaces in Contact? Scale: Visible Force: Gravity Tools: Eyes 3. What Are Your Ideas About Small Sizes? Scale: Visible/Invisible Dominant Force: Varies Tools: Eyes, Instruments 1. How Can a Gecko Walk on a Ceiling? Scale: Visible Dominant Force: Gravity Tools: Eye 5. What Types of Forces Can Hold Objects Together? Scale: Visible/Invisible Dominant Force: Gravity Tools: Eyes and Hands 4.What Do We Learn When We Look More Closely? Scale: Invisible Dominant Force: Extremely Small, Large in Number Tools: Special instruments (scanning tunneling microscope)

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