1
Rotational Kinetic Energy
RKE
Rotational Kinetic
Energy
revised July 11, 2005
Learning Objectives:
During this lab, you will
1.
communicate
scientific
results
in
writing.
2.
estimate the uncertainty in a quantity
that is calculated from quantities that
are uncertain.
3.
be
introduced
the
Monte
Carlo
Simulation method.
4.
test a physical law experimentally.
A.
Introduction
You will use the principle of conserva-
tion of energy to determine the moment of
inertia of a system of four identical masses
symmetrically located on the circumference
of a wheel which is rotating about its axis
(Figure 1). You will compare the value you
measure to the value you calculate from
theory.
Because the wheel has a complicated
shape, you must measure rather than calcu-
late its moment of inertia. You can also
measure the combined moment of the wheel
and the mass loads and then calculate the
moment of inertia of the loads alone as the
difference between these two measurements.
This experiment also includes an intro-
duction to a numerical method that may be
new to you - Monte Carlo computer simula-
tions. Monte Carlo simulations are used to
study phenomena where random chance is
expected to play a major role. Randomness
is also a feature of the experimental errors
than one often encounters. You will use a
Monte
Carlo
simulation
for
the
RKE
experiment to create data for debugging and
testing your analysis routine. You will then
apply this analysis routine to experimental
data collected from the inertia wheel and
mass loads.
You must write a report for this lab
worth 60 points.
B.
Apparatus
Neighboring groups will share a single
setup, but each group must acquire and ana-
lyze their own set of data. It takes very little
time to take the data you need for this
experiment so sharing a single setup should
not be a problem. Before taking any data, be
certain that the cable from the encoded pul-
ley is plugged into the jack on your own
computer station.
The key piece of apparatus is a
Roto-
Dyne
inertia wheel [
mass M
R
= 1.5 kg,
radius r = 0.200±0.002 m
] on which you
can mount four cylindrical mass loads [
M
L
=
0.225±0.002 kg each
]. The torque necessary
to rotate this wheel will be supplied by grav-
ity acting on a hanging mass [
M = 60 g
] and
some paper clip masses,
m
. You will also
use a meter stick, an encoded pulley and a
computer running the
Logger Pro
program.
The experimental setup is illustrated in
Figure 1. The hanging mass
M
is tied to a
string hanging over an encoded pulley and
wrapped around the grooved circumference
of the wheel. The encoded pulley records
Encoded Pulley
Roto-Dyne inertia wheel
W=Mg
Loads
Loads
Figure 1:
Experimental Arrangement

This
** preview**
has intentionally

**sections.**

*blurred***to view the full version.**

*Sign up*