PASCO ME-8950A COMPLETE ROTATIONAL SYSTEM - Manual (Page 35)

012-05293F Complete Rotational System
31
Experiment 5: Rotational Inertia of Disk and Ring
EQUIPMENT REQUIRED
- DataStudio Program - Mass and Hanger Set
- PASCO Interface (see Note) - Paper Clips (for masses < 1 g)
- Rotational Inertia Accessory (ME-8953) - Balance
- Photogate/Pulley System - Calipers
Purpose
The purpose of this experiment is to find the rotational inertia of a ring and a disk experimentally
and to verify that these values correspond to the calculated theoretical values.
Theory
Theoretically, the rotational inertia, I, of a ring about its center of mass is given
by:
where M is the mass of the ring, R
1
is the inner radius of the ring, and R
2
is the
outer radius of the ring. See Figure 5.1.
The rotational inertia of a disk about its center of mass is given by:
where M is the mass of the disk and R is the radius of the disk. The rotational inertia of a disk
about its diameter is given by:
To find the rotational inertia experimentally, a known torque is applied to the object and the
resulting angular acceleration is measured. Since
τ = Iα,
I
1
2
---M R
1
2
R
2
2
+ ( ) =
I
1
2
---MR
2
=
I
1
4
---MR
2
=
I
τ
α
--- =
Figure 5.1: Ring
R
1
R
2
R
Disk about center of Mass Disk about Diameter
R
Figure 5.2:
Note: If you are
using a PASPORT
interface, you will
also need a Digital
Adapter (PS-2159)