What Do We Learn When We Look More Closely? 1 © 2009 McREL Physical Science Lesson 4 What Do We Learn When We Look More Closely? Investigating Static Forces in Nature: The Mystery of the Gecko

What Do We Learn When We Look More Closely? 2 © 2009 McREL Observing Surfaces Consider the following surface interaction: –Transparent tape on lab table Diagram and describe what is happening between the two surfaces. Image 4.6

What Do We Learn When We Look More Closely? 3 © 2009 McREL Adhesives What did you do to ensure that the sticky side of the tape had the most contact with the desk? Describe how your tape on the desk resisted removal. Is this a property of a liquid or solid?

What Do We Learn When We Look More Closely? 4 © 2009 McREL Compliant Surfaces Soft – Transparent Tape Hard – Desk Top If one or both surfaces are compliant: Hard – Shoe hard If both surfaces are hard: Only a small percentage of the apparent contact area is in real contact. Image 4.3Image 4.4 apparent contact area real contact area A large percentage of the apparent contact area is in real contact.

What Do We Learn When We Look More Closely? 5 © 2009 McREL Prediction Predict (using words and drawings) what you think the surface of the gecko’s foot looks like as we magnify the foot. Image 4.5 Image 4.6

What Do We Learn When We Look More Closely? 6 © 2009 McREL Gecko Foot “Up Close” Kellar Autumn Each spatula is about 100 nanometers thick. Image 4.7

What Do We Learn When We Look More Closely? 7 © 2009 McREL Making Connections 1.Describe one or two ideas that you learned during this lesson. 2.Which range do gecko setae fit into? 3.Which force would make best use of these many points of contact?

What Do We Learn When We Look More Closely? 8 © 2009 McREL Flow Chart 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? 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) 7. How Do We Measure Forces at the Nano Level? 8. How Can a Gecko Walk on a Ceiling? 6.How MUCH Force Is Needed to Make an Object Stick? What Factors Affect the STRENGTH of Force Acting?

What Do We Learn When We Look More Closely? 9 © 2009 McREL Sample Student Drawings

What Do We Learn When We Look More Closely? 10 © 2009 McREL Sample Student Drawings

What Do We Learn When We Look More Closely? 11 © 2009 McREL Sample Student Drawings