Lab #9: Moment of Inertia
Theory:
Explain analogy between linear and rotational motion. What is moment of inertia?
Moment of inertia of a single particle and system of particles. Moment of inertia of a
bar. Experimental moment of inertia.
Experiment: To determine an experimental value of I for a rectangular bar, we will
determine I for the platter (moment of inertia apparatus) both with and without the
rectangular bar. We can then subtract the value of I for the platter without the bar from
the value of I for the platter with the bar to obtain I for the bar.
Just a platter
1. Determine the mass needed to overcome force on the system due to friction (mf)
using paper clips. δm f is the mass of one paper clip.
2. Plot V vs. t for the platter using mh = 70g. Slope of that line is measured
acceleration. Repeat for a second set of data.
3. Calculate Ipl using
g
I pl = mR 2 ( − 1)
a
m=mh-mf mh-hanging mass
Platter and the bar: Repeat steps 1 through 3
g
− 1)
a
Calculate 4 values for Ibar using Ibar=Itot-Ipl
Calculate the average Ibar and statistical uncertainty
4
I 1 + ...... + I bar
I bar = bar
4
σ
δI bar =
4
Calculate Itheory±δItheory using
1
I theory = M ( a 2 + b 2 )
12
M-mass of the bar
a-bar length
b-bar width
Compare Ibar with Itheory
I tot = mR 2 (
4.
5.
6.
7.