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Abstract
Moment of inertia, also called mass moment of inertia, is a measure of an object's resistance to changes to its
rotation. It describes the difficulty encountered in bringing the body to angular rotation about a specified axis
of rotation. When an object rotates about an axis it exhibits moment of inertia, the moment of inertia differs
with the axis of rotation and the size and mass of the body being rotated. In the experiment the moment of
inertia of a disk and a ring is measured. The experiment also compared the moment of inertia of the disk at two
different axes.
Introduction
Moment of inertia measures the rotational inertia of
a rigid body. It is the quantity telling how difficult it
is to rotate a given body. Moment of inertia can be
expressed in two forms, the scalar or the tensor.
The moment of inertia of an object about a given
axis describes how difficult it is to change its
angular motion about that axis. Therefore, it
encompasses not just how much mass the object has
overall, but how far each bit of mass is from the
axis. The farther out the object's mass is, the more
rotational inertia the object has, and the more force
is required to change its rotation rate.
In determining for the index of refraction of
materials, calculations were done using the law of
refraction
(also
known
as
Snell’s
Law):
=
n1sinθ1 n2sinθ2
; where n is the index of
refraction of the material, and
θ
is the angle of
incidence. The subscripts 1 and 2 denote the first
and second material respectively. The formula was
obtained from the textbook; University Physics by
Young and Freedman.
In determining for the critical angle of the total
internal reflection, Snell’s law was also used, only
this time the angle of incidence for the second
medium was taken to be 90° because for TIR,
should the incident light reflect within the second
material, the angle of reflection with respect to the
incident light would be 90°. From there, the angle
of incidence with respect to the normal line could
be obtained.
For the experimental value, however, an application
of trigonometry was used, where the point at which
the total internal reflection was obtained, and the
distance from the corner of the glass plate to the
point, as well as distance of the point parallel to the
point of reflection. From here, the tangent function
was used, giving the critical angle
θ
c
= tan
1
(o/a);
where o is the opposite side of the critical angle,
and a is the adjacent side of the critical angle.
Methodology
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This note was uploaded on 05/29/2011 for the course PHYS 11L taught by Professor Deleon during the Spring '11 term at Mapúa Institute of Technology.
 Spring '11
 DeLeon
 Physics, Resistance, Inertia, Mass

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