how much force is needed to make an object stick? 1 © 2009 mcrel physical science lesson 6 how much...

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


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What’s Happening?

What can be said about the forces that are affecting the shoe?

Image 6.1

Image 6.2


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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


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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?


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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


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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.


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Measuring Forces

• How are forces measured?

• Unit: Newton

• Instrument: Spring Scale

http://sciencekit.com/dual-calibration-spring-scales/p/IG0025724/

Image 6.5


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Measuring Forces

• Consider the following question:– How could one measure the amount of “stickiness”

of a piece of tape on a tabletop?


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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


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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


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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?


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Flow ChartFlow Chart

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

7. How Do We Measure Forces at the Nano Level?

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

8. How Can a Gecko Walk on a Ceiling?

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

Scale: InvisibleDominant 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?

how much force is needed to make an object stick? 1 © 2009 mcrel physical science lesson 6 how much...

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