how can a gecko walk on a ceiling?1 © 2009 mcrel physical science lesson 8 how can a gecko walk on...

How Can a Gecko Walk on a Ceiling? 1© 2009 McREL

Physical ScienceLesson 8

How Can a Gecko Walk on a Ceiling?

Investigating Static Forces in Nature:

The Mystery of the Gecko


Closer LookImage 8.3 Spatula-Shaped Tips

Image 8.2 One Gecko Seta


Tape and Spatula

(d)

1 mSpatula-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


What Is Happening Between The Surfaces?

• Play the “Hot Spots” Game to find out!http://dawn.jpl.nasa.gov/mission/ion_engine_interactive/lev2/index.html

Or• Charge Simulator:

http://dawn.jpl.nasa.gov/mission/ion_engine_interactive/lev1/index.html

• How does the kind of charge on the particle affect the deflection of the positively charged particle?


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?


Type of Interaction


Questions

4. What makes you think that these attractions are weak?

5. Are these permanent or temporary attractions? How long do they last?


++

- +++ +++

-

-

--

--

-

++

- +++ +++

-

-

--

--

-

Image 8.8 Image 8.9

Describe the Interaction


++

- +++ +++

-

-

--

--

-

++

-+++ +++

-

-

--

-

--

Image 8.10 Image 8.11

Describe the Interaction


Weak/Temporary Interaction Between Two Surfaces

Image 8.14

– + – +

Image 8.15

Image 8.13

Image 8.12

Single Gecko Seta

Probe Surface


Animation


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?


• 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?


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.


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: VisibleForce: Gravity, AdhesiveTools: Spring Scale

2. What Do We Mean When We Speak About Surfaces in Contact?

Scale: VisibleForce: GravityTools: Eyes

3. What Are Your Ideas About Small Sizes?

Scale: Visible/InvisibleDominant Force: VariesTools: Eyes, Instruments

1. How Can a Gecko Walk on a Ceiling?

Scale: VisibleDominant Force: GravityTools: Eye

5. What Types of Forces Can Hold Objects Together?

Scale: Visible/InvisibleDominant Force: GravityTools: Eyes and Hands

4. What Do We Learn When We Look More Closely?

Scale: InvisibleDominant Force:

Extremely Small, Large in Number

Tools: Special instruments (scanning tunneling microscope)

how can a gecko walk on a ceiling?1 © 2009 mcrel physical science lesson 8 how can a gecko walk on...

Documents