Rubber Band Stretching

Analysis

	To analyze our videos and determine the maximum amount of horizontal stretch per trial we used the

Tracker program. During the experiment we shot a clip of a ruler so that we could use its width to scale all the

video clips to size. We were able to use this scale in all trials because we never changed the camera 

placement. With the scale in place, we set the origin at the initial position of the rubber band before being hit

by the bullet. We went through the clip frame-by-frame and placed a marker at the horizontal maximum of each

frame.  Tracker then made a graph of horizontal distance traveled versus time, which appeared quadratic. Once

the rubber band reached its maximum horizontal stretch for the entire clip, we recorded the data. 

	We used Graphical Analysis to make a graphical interpretation of our data. Our independent variable (x)

was the vertical stretch, while the dependent variable (y) was the horizontal stretch, which we determined using

Tracker software. We then had a graph of horizontal stretch vs. vertical stretch. We also created a second graph

by averaging the vertical stretch of each trial, and averaging the horizontal stretch of each trials. This gave us a 

clearer picture of what was going on. 

A clip of a rubber band at its maximum horizontal stretch after being hit by a BB. (Captured by the MotionScope 8000S)

A screenshot of Tracker analysis. The blue diamonds track maximum horizontal stretch of each frame. The red axes are centered at the origin. The graph to the right plots horizontal position versus time.

A screenshot of our data in Graphical Analysis. The bottom right hand graph represents average horizontal stretch versus the average vertical stretch per trial. The top graph has all data points from each individual trial.