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

“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

Slide from Week 5

After Normalizing “stretch”

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: – results comparing analysis and experimentation

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

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

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

To yield Two versions: –Linear model –Cubic model

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

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

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