Length of Rubber band Pre-stretch (cm)
Black
1
2
3
4
5
Red
Green
1
18.3 ±.05
18.9 ±.05
18.5 ±.05
2
17.8 ±.05
17.5 ±.05
16.45 ±.05
3
17.1 ±.05
18.35 ±.05
14.55 ±.05
4
17.1 ±.05
21.4 ±.05
18.7 ±.05
5
15.2 ±.05
16.65 ±.05
17.7 ±.05
Length of Rubber band Post-stretch (cm)
Black (0 min)
Red (5 min)
Green (10 min)
20.4 ±.05
19.1 ±.05
20.4 ±.05
18.6 ±.05
18.5 ±.05
18.4 ±.05
18.2 ±.05
20.2 ±.05
17.4 ±.05
18.6 ±.05
22.4 ±.05
19.6 ±.05
15.7 ±.05
18.3 ±.05
19.2 ±.05
Average Length of rubber band pre-stretch (cm)
Black
17.1 ±.05
Green
18.56 ±.05
Red
17.18 ±.05
Average Length of rubber band post-stretch (cm)
Black
18.3 ±.05
Green
19.7 ±.05
Red
19 ±.05
Average found using:
𝑘
1
∑ ( ∗ 𝑋𝑛 )
𝑘
𝑛=1
k = number of trials
n = trial number
X = measured value
This summation is used to find the average value of each set of trials. This particular formula
accommodates for any number of values, rather than making a specific formula for each set of values.
∆length (post-pre stretch in cm)
Black
1.2 ±.15
Green
1.14 ±.15
Red
1.82 ±.15
Uncertainty doubles in this case due to the subtraction of two values (each) with uncertainty of 0.5. At
the same time, uncertainty is increased by 0.05 to accommodate for potential rubber band stretch from
measurement. Lengths are also doubled because only half of the rubber band was measured, producing
a graph like this:
Time rubber band stretched vs difference
between final and initial length
2.5
2
Length (cm)
10, 1.82
1.5
0, 1.2
5, 1.14
1
0.5
0
0
2
4
6
Time (minutes)
8
10
12
The average difference value for no stretch rubber band is higher than that of the 5 minute average. This
is a result of one of the rubber bands being weighted by the 305g for an extended period of time on
accident. This resulted in stretch that influenced the result, yielding a stretch of 2.1cm whereas others of
the same set yielded much less, approximately 1cm. These are the results if we remove the outlier from
consideration.
Real ∆length (post-pre stretch in cm) sans outlier
Black
0.975 ±.3
Green
1.14 ±.3
Red
1.82 ±.3