of Mass a Yardstick
The goal of this exercise is for your group to predict the mass of a yardstick. If the actual mass lies
within your predicted range, you win! (What? Well my respect, for one thing, bragging rights for
another.)
It may sound easy, but here's the problem: you are not allowed to examine or touch the yardstick in
question before making the prediction. Instead, you have access to the following:
five pieces of a broken yardstick (which do not add up to an entire yard)
a triple-beam balance scale
a ruler
some graph paper
the knowledge that an intact yardstick is one yard long.
To start, please fetch a triple-beam balance scale for your group. Choose a single piece of stick and
practice using the scale to measure its mass. When you are comfortable using the balance, start
measuring the other pieces and record the mass of each one.
Some things to consider:
what other measurement will you need to make?
how will you estimate the error on each measurement?
how will you use your to data estimate the mass of the stick?
Hint1: if you can figure out the linear mass density of the stick (that is, the mass per millimeter or
centimeter), then you can compute the mass of any given length.
Hint2: if you know the uncertainty in the linear mass density, then you can compute the uncertainty in
the mass of any given length.
What you must hand in
Each group must submit the following materials (just one set per group, not one per student)
a cover page including a title, the date and the names of the group members
a neat table of all measurements
a page which shows one example of each type of calculation (but not all the calculations)
a good, clear graph
the predicted mass (with uncertainty) and actual mass (with uncertainty)
a sentence or two explaining the results did the predicted mass agree with the actual mass to
within the predicted uncertainty?
your (brief) assessment of the largest single source of error in the experiment, and how it could
be reduced next time.
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