1. How MUCH Force is Needed to Make an Object Stick? 1 © 2009 McREL Physical Science Lesson 6 How MUCH Force Is Needed to Make an Object Stick? What Factors Affect the AMOUNT of Force Acting on an Object? Investigating Static Forces in Nature: The Mystery of the Gecko

2. How MUCH Force is Needed to Make an Object Stick? 2 © 2009 McREL What’s Happening? What can be said about the forces that are affecting the shoe? Image 6.1 Image 6.2

3. How MUCH Force is Needed to Make an Object Stick? 3 © 2009 McREL Consider the Ant The weight of this ant is 0.00004 Newtons. http://ant.edb.miyakyo-u.ac.jp/Taxo_E/F80706.html Image 6.3

4. How MUCH Force is Needed to Make an Object Stick? 4 © 2009 McREL Imaginary Animal Imagine an animal who is larger in every dimension and whose mass and volume is ten times larger than the ant. The weight of this imaginary animal is 0.0004 Newtons. How many “ant feet” (points of contact) would be required for this animal to adhere to the ceiling?

5. How MUCH Force is Needed to Make an Object Stick? 5 © 2009 McREL Gecko Let’s return our attention to the gecko. Repeat your calculations from the imaginary animal for a Tokay Gecko, with an average weight of 2.2 Newtons. Image 6.4

6. How MUCH Force is Needed to Make an Object Stick? 6 © 2009 McREL Separation Force Vs. Adhesion Adhere (adhesion force) is the amount of force required to hold objects together. Separation force is the amount of pull that is required to detach two objects.

7. How MUCH Force is Needed to Make an Object Stick? 7 © 2009 McREL Measuring Forces How are forces measured? Unit: Newton Instrument: Spring Scale http://sciencekit.com/dual-calibration-spring-scales/p/IG0025724/ Image 6.5

8. How MUCH Force is Needed to Make an Object Stick? 8 © 2009 McREL Measuring Forces Consider the following question: –How could one measure the amount of “stickiness” of a piece of tape on a tabletop?

9. How MUCH Force is Needed to Make an Object Stick? 9 © 2009 McREL Measuring Forces Question: How does the amount of dirt affect the amount of force required to lift a piece of tape from a glass microscope slide? Materials: –Transparent tape –Duct tape –50 N spring scale –Hole punch –Ruler, protractor Image 6.7

10. How MUCH Force is Needed to Make an Object Stick? 10 © 2009 McREL Experiment: Measuring Adhesion Image 6.8Image 6.9

11. How MUCH Force is Needed to Make an Object Stick? 11 © 2009 McREL Just Add Water… “Also, the scientists discovered that the gecko adhesive works in a vacuum and underwater, leaves no residue and is self-cleaning.” “Tape gets dirtier and dirtier with repeated use,” Autumn notes. “However, a gecko’s foot gets cleaner and cleaner.” The scientists clogged the gecko hairs (on the surface of the feet) with submicron particles, but five steps later the hairs were clean. “We don’t know how geckos do that, but it is so amazing that we are working hard to figure it out,” Autumn says. http://www.lclark.edu/dept/public/chrn_geckopower.html

12. How MUCH Force is Needed to Make an Object Stick? 12 © 2009 McREL Making Connections 1.Describe one or two ideas that you learned during this lesson. 2.What factors contribute to the amount of force to remove a sticky substance? 3.How does dirt affect adhesion? 4.Do you think that a sticky substance is a possible method for the gecko adhesion? 5.How do you think the gecko sticks to the ceiling? 6.What should we explore next?

13. How MUCH Force is Needed to Make an Object Stick? 13 © 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 7. How Do We Measure Forces at the Nano Level? 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 8. How Can a Gecko Walk on a Ceiling? 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) 6. How MUCH Force Is Needed to Make an Object Stick? What Factors Affect the STRENGTH of Force Acting?