1. EGR 105 Foundations of Engineering I Fall 2005 – week 10 Project time

2. “Normalization” Last time we noted that different cord lengths yielded different stretch vs force relationships Hopefully you found that normalizing (i.e. dividing) the stretch by the original length of the cord produces a consistent plot

3. Slide from Week 5

4. After Normalizing “stretch”

5. Today’s Activities Test a short jump/drop, comparing analysis and experimentation: –Analysis using earlier physics discussion (detailed on the next few slides/handout) –Experimentation using your cord and a simple mass in a series of short jumps (4-6’) Assignment 8: –E-mail results comparing analysis and experimentation

6. Analysis Recall physics (Week 3): –At the top, potential energy only –At the bottom, energy stored in the cord –Parameters: d 0 = drop distance m = mass L = cord length

7. At the Bottom, distance d 0 Velocity v is now zero, so We could solve for d 0 if we knew f – and now we do!! v = 0 d0d0 L

8. But f depends upon L, so we use the normalized version and change variables

9. To yield Two versions: –Linear model –Cubic model

10. Example, Linear Cord If then we have or the quadratic equation

11. Example, Cubic Cord If then we have Can solve numerically (HW4, prob 3)

12. Today – in class Experimentation: –Choose mass m and cord length L –Aim for 50-150% stretch –Measure drop distance d 0 (average several drops) Repeat for a second m, L choice Compare to analysis results Turn in hard copy E-mail results to me in your e-notebook