You must submit this report by the referred work deadline. You must show all working. Note
that this is an individual assignment.
In order to complete this part of the assignment you should refer to the laboratory sheet on SunSpace
concerning the calculation of inertia of a flywheel. You are not required to do the experiment or
write up the introductory parts of the report. However you should analyse the data provided below
as if you had obtained it by doing the experiment and write up your report accordingly.
During the course of the experiment a set of weights were hung in turn on a piece of cord from a
pulley attached to the flywheel. The objects were allowed to fall under gravity from a height of 1
metre, as described in the laboratory sheet. This was performed three times and the data recorded is
shown in the table below. The diameter of the spindle d (= 2r) was found to be 38 mm (0.038 m).
Total weight
(including hanger)
1st descent
2nd descent
3rd descent
3.2 29.69 34.60 34.60
6.0 24.25 24.28 25.22
8.5 19.60 19.70 19.95
11.0 17.60 17.06 17.29
13.5 15.12 15.65 15.12
Complete the following tasks:
a) The flywheel dimensions are as follows: diameter = 390mm, mean thickness = 30mm. Also, it is
made of steel, with density 7850 kg/m3. Use this information to estimate the inertia, by
considering the formula for the inertia of a solid disc. This value should be used as an
approximate validation of the inertia derived in part (b). (30%)
b) Analyse the tabulated data and use it to determine the inertia of the flywheel and the frictional
torque Tf. You should use Excel to calculate and tabulate relevant values, and to plot P? r
versus a, as per the laboratory sheet. (70%)
NB: do not confuse weight with mass (a common mistake!)

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