Rubber Band Lab
Research Question
The aim of the experiment is to investigate the relationship between quantity of rubber
bands and weight required to extend the rubber bands to a given length. This will be done by
changing the quantity of rubber bands and measuring the weight required to extend the rubber
bands to a desired distance of 12cm.
The same type of rubber bands will be used along with the same set of weights along
with weight holder. The set up will remain the same throughout all trials. It is expected that an
increase in the number of rubber bands will correspond to an increase in the weight required to
stretch the rubber bands to the given distance of 12cm.
Variables
Independent: Number of rubber bands.
Dependent: Weight required to stretch the rubber bands, measured in grams.
Controlled: Rubber band type, weight holding device, position of tape measure, and the position
of the rubber bands, distance.
Materials
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Five rubber bands
Five 5g weights
Five 20g weights
Five 10g weights
Three 50g weights
Three 100g weights
One weight holding device (3g)
One 152cm tape measure
One 10cm long metal rod
One 100cm tall table
One roll of duct tape
Apparatus
Attach the 10cm long metal rod to the top of the 100cm tall table using duct tape,
ensuring that one end of the metal rod extends beyond the end of the table and rubber bands may
easily hand from it. Secondly, attach the 152cm tape measure to the table such that the first
measurement mark is at the top of the table and the tape measure is hanging off of the side of the
table.
Method
1.
2.
3.
4.
5.
Set the testing apparatus as described above.
Place one rubber band onto the metal rod.
Attach the weight holding device.
Place weight onto the weight holding device, increasing in increments of five grams.
Measure the length of the rubber band with the added weight, measurement is taken at the
end of the rubber band and not the weight holding device while ensuring the
measurement is taken while facing the tape measure perpendicularly.
6. Repeat steps 3-5 using two, three, four, and finally five rubber bands.
Raw Data
Rubber
Bands
1
2
3
4
5
Mass (g)
± 5g
1st Trial
65
95
135
170
250
2nd Trial
65
90
125
170
225
3rd Trial
60
95
120
175
220
4th Trial
60
85
125
180
220
5th Trial
55
80
120
165
215
Average
61
89
125
172
226
250
5, 230
5, 225
5, 220
200
4, 172
y = 44.1x - 0.5
Low Slope
150
High Slope
Average
3, 127
Linear (Low Slope)
100
Linear (High Slope)
2, 89
Linear (Average)
1, 51
1, 46
1, 41
50
0
0
1
2
3
4
5
6
The low slope has a gradient of 42.25, the high slope has a gradient of 47.25 and the gradient of
the line of best fit is 44.1.
The uncertainty above the best fit line is 47.25 - 44.1 = 3.15
The uncertainty below the best fit line is 42.25 - 44.1 = -1.85
The gradient and uncertainty of the line of best fit are 44.1 (+3.15)/(-1.85)
Conclusion
Based on the gradient and equation of the line of best fit it can be determined that an
increase in rubber bands does result an increase in weight required to extend the rubber bands to
12cm. The relationship between number of rubber bands and weight required for extension is a
linear one. However, because the equation of the line of best fit does not pass through the origin
it is not a proportional relationship.
Evaluation and Improvements
Even though the relationship is linear, the errors involved are significant. The error is due
to an imprecise method of measuring when the rubber band was extended to 12cm. Once it
appeared to be extended to the 12cm an additional weight not exceeding 5g could be added and
the rubber band would not extend to a measurable degree. Because of this it was decided to
utilize a maximum uncertainty of ± 5g. This uncertainty represented the most extreme variance
in weight that would not a measurable change in the extension of the rubber band.
The most significant improvement that could be made to the experiment is a more precise
method of measurement. A measurement system with greater precision would help to decrease
uncertainty and move trial results closer together, ensuring that the averages reflect to a greater
degree the actual value. If this was done it is highly likely that the relationship between rubber
band number and weight required for an extension of 12cm would be found to be proportional.
This is due to the fact that using an unreliable method of measurement in this experiment the
equation of the line of best fit was found to be y = 44.1x - 0.5, a nearly proportional relationship.