1. Wed. May 4– Physics Lecture #6 Strength of Plant Materials 0. Announcements, Innovators Presentations 1.Life of a Leaf discussion 2.Stress and Strain 3.Young’s Modulus 4.Shear Modulus 5.Bulk Modulus Uncredited images from OpenStax College Physics

2. 0. Announcements, Innovators Presentations

3. 1. Life of a Leaf discussion

4. 3.Stress and Strain

5. The graph represents the stress versus strain for a particular material. What do you notice about this graph? What is the slope of the stress-strain curve in the elastic region?

6. 4. Young’s Modulus

7. Consider an aluminum wire and a steel wire, each of the same length and diameter. A 10 kg mass is hung from the end of each wire. Which wire will undergo the bigger elongation? 1.Aluminum wire 2.Steel wire 3.Same elongation 4.Not enough information

9. Steel beams are used for load bearing supports in a building. Each beam is 4.0 m long with a cross-sectional area of 6.9 x 10 –3 m 2 and supports a load of 6.7 x 10 4 N. Young's modulus for steel is 210 x 10 9 N/m 2. a)How much compression does each beam undergo along its length? b)Determine the maximum load one of these beams can support without any structural failure. Assume the compressive strength of steel is 1.50 x 10 8 N/m 2.

10. 5. Shear Modulus

13. 6. Bulk Modulus