1. © 2010 Pearson Education, Inc. Conceptual Physics 11 th Edition Chapter 12: SOLIDS

2. © 2010 Pearson Education, Inc. This lecture will help you understand: Density Elasticity Tension and Compression Arches No Warm-Up. Lets gets started so we can move into lab. You will be building a bridge using toothpicks

3. © 2010 Pearson Education, Inc. Density-Density depends upon mass of the atoms, spacing between the atoms. Density is a property of the material—it does not matter how much material you have. Amount of mass per unit volume of a material. Unit of density is kg/m 3 or gm/cm 3. Example: Density of water is 1000 kg/m 3, or 1 g/cm 3. Is also sometimes expressed as weight density. Unit of weight density is N/m 3. volume mass Density  2 densitym/s9.8densityWeight   volume weight densityWeight 

4. © 2010 Pearson Education, Inc. Elasticity An object subjected to external forces may undergo changes in shape and/or size. Due to arrangement and bonding of atoms. A body’s elasticity is a measure of how much it changes when a deforming force is exerted on it and how well it returns to its original shape. –Materials that do not return to their original shape are inelastic.

5. © 2010 Pearson Education, Inc. Elasticity Hooke’s law: The extension of a spring is directly proportional to the force applied to it. extension ~ Force or x ~ F 

6. © 2010 Pearson Education, Inc. Tension and Compression When something is pulled it is in tension. squashed it is in compression. tension Compression tension The blue line is the “neutral layer”

7. © 2010 Pearson Education, Inc. Tension and Compression. Less material needed

8. © 2010 Pearson Education, Inc. Tension and Compression

9. © 2010 Pearson Education, Inc.

10. Exit Ticket HW: Chapter 12 –Review Questions pg 224 #7, 8, 12, 16 –Exercises pg 225 # 6, 8, 9, 10, 21, 27

11. © 2010 Pearson Education, Inc. Which is more elastic—steel or rubber? A. Steel B. Rubber C. They are equally elastic. D. Not enough information. A 10-cm-long spring extends to 12 cm when a 1-kg load is suspended from it. What would be its length if a 3-kg load were suspended from it? A. 14 cm B. 16 cm C. 20 cm D. 24 cm Suppose you drill a hole horizontally through a tree branch as shown. Where will the hole weaken the branch the least? A. Near the top B. Near the bottom C. Near the middle D. It does not matter Review for Chapter 12