Physics 1 (SCIH 035 058)
Creating a Mass Scale
with Elastic Materials
This project is worth 9% of your overall grade for this course. Be sure to read all the instructions and
assemble all the necessary materials before you begin. You will record your data and insert your
answers in the Project Write-up section of this project. When you have completed this project you
may submit it electronically through the online course management system. Check the instructions in
the online course for more information.
Construct and calibrate a mass scale with simple materials and test its accuracy, precision, and
Since you have completed the Tension Lab Activity in Lesson 7, you should have a good
understanding of the way rubber bands respond under various amounts of tension.
Use the knowledge you gained from the Tension Lab Activity in Lesson 7 to
create and calibrate a scale capable of accurately measuring the mass of a
variety of objects.
You may use rubber bands or any other elastic material but you may not use
any components made for use as part of a commercially available scale or
balance (one that you buy already constructed) in your scale construction.
Decide what range of masses you intend to measure. Suggestions include:
1 – 10 g
5 – 50 g
10 – 100 g
1 – 100 g
5 – 500 g
Note that if you are building a scale that will function over a large range of
masses, you may need to build separate components (one part to measure
masses between 1 and 10 grams and a separate part to measure masses
between 10 and 100 grams.
Decide what accuracy your scale should have (accuracy is ability to measure
the CORRECT value). No matter what mass you are measuring, you should
not be more than 5% off. Calculate the % error. % Error = ((actual mass –
measured mass) / actual mass) * 100%
Decide what precision your scale should have (precision is the ability to give
the same measurement for a mass, time after time. If you place a 5 gram
mass on the scale three separate times, the readings should be the same
each time to within +/- so many grams. As with accuracy, smaller masses
should have smaller variances between readings. Precision is usually
reported as the range / 2. Range is easily calculated by “highest
measurement – lowest measurement.” The final answer is given as “average
measurement +/- precision.”
Calibrate your scale. Use a series of known masses to calibrate your scale.
Use masses near the low end, the middle, and the high end of your working
range. You cannot assume that your scale will respond equally to the addition
of each mass. Record your work in the data tables provided. You may add
space or pages to the Project Write-up section if you need them.
Test your scale. Use a series of known masses to check the function of your
scale. This will feel similar to the calibration but this actually a separate step.
The way your elastic material behaves may change over time and so you may
not get the same readings that you did at the beginning of your calibration.
Think of how a sweater “stretches out” as you use it—similar things happen to
Use at least 3 masses, one near the low end, one at the middle and one near
the high end of your working range. For each mass, test it at least three times
to measure accuracy and precision.
Make at least one significant change to your scale to improve its performance.
If the performance of your scale did not meet your expectations, make a
change to the way it is constructed or the materials you are using. If it already
met your design parameters, make a change to increase its performance
capabilities (allowing it to measure a wider range of masses, for example.
Repeat your test measurements record your data in a table then analyze your
results. Did you improve the performance of your scale? If so, by how much?
Suggest additional changes that could improve the performance of your scale
Fill in the following tables and answer the following questions. Don’t forget to use the Grading Rubric
as a guide to gauge how effectively you complete this portion of your project.
Prediction (what your scale is
designed to do)
Chosen (be specific,
what kind, what
size, how many,
Working Range of
Accuracy of Scale
(calculate % error)
Precision of scale
as +/- half the
Performance (what you scale
5. (5 pts) Construction: (Describe how your scale is constructed and include a diagram or picture.)
6. (5 pts) Calibration Procedure: Describe the process you used to calibrate your scale. Create a
table that shows what masses were used, and how you measured the change in your scale with
7. (20 points) Test Data: you have designed your scale to perform in a certain way, but you need to
test it against known masses to see if it is performing as desired. Remember that you are testing
each of three masses three times.
% Error = ( (measured mass – actual mass) / actual mass) * 100%
8. (5 pts) Based on your test data, write a statement describing the accuracy of your scale at each
9. (5 pts) Based on your test data, write a statement describing the precision of your scale at each
10. (5 pts) What change did you make to improve the accuracy / precision of your scale?
11. (20 points) Test Data (Round 2)
12. (5 pts) Based on your test data, what is the accuracy of your scale? How close are you the real
value for each mass?
13. (5 pts) Based on your test data, what is the precision of your scale? How close are each of your
measurements to each other?
14. (5 pts) Suggestions for additional improvements. What changes do you suggest and why do you
think they would be helpful?
Total = 100 pts
Meets minimum project
Does not meet
Description is clear and
thorough. A working
device could be
constructed from these
instructions. A detailed
picture is included
showing scale and
Description is fairly detailed but
lacks some specifics like size,
scale, materials, etc. A picture
is included but could be more
detailed. A device might be
constructed from these
instructions but may not be the
same as the one used.
Cannot tell how device was
information given. Picture is
missing or is not
informative. Cannot tell
what materials were used,
their size or how they are
does not reflect
is missing or is not
Calibration was clearly
covered low, middle, and
high end of range,
repeated to ensure
Calibration was done and
measurements covered low,
middle and high but may not
have been repeated or may
have given unreliable results.
Calibration was done but
Calibration was not
measurements do not cover done according to
entire range and were not
repeated. No confidence in
reliability of measurements.
Data is compiled and
provided as directed and
Calculations of %Error,
accuracy, and precision
Data is compiled and provided
as directed but calculations
may be incorrect. Accuracy
and precision may need to be
Data is not complete. Some
calculations are missing or
incorrect. Cannot determine
accuracy or precision.
Data is not
complete. Data is
not compiled and
suggested and made.
Data clearly shows
change in accuracy or
An improvement was
suggested and made. May not
see clear change in accuracy
Improvement was not
reasonable or data does not
show change in accuracy or
made or data does
not show change in
Questions are answered
thoroughly and with
evident self -reflection.
Project was completed and
questions were answered but
could have shown more
thoughtfulness or self
Project is completed to
Questions are answered but
are not thoughtful. Student
does not demonstrate self
Project is not
This project can be submitted electronically. Check the Project page under “My Work” in the
UNHS online course management system or your enrollment information with your print
materials for more detailed instructions.
Purchase answer to see full