Experiment 3: conservation of angular momentum – PASCO CI-6538 Rotary Motion Sensor User Manual
Page 28
®
Model No. CI-6538
Rotary Motion Sensor
27
Experiment 3: Conservation of Angular
Momentum
Purpose:
A non-rotating ring is dropped onto a rotating disk, and the final angular
speed of the system is compared with the value predicted using conservation
of angular momentum.
Theory:
When the ring is dropped onto the rotating disk, there is no net torque on the
system since the torque on the ring is equal and opposite to the torque on the
disk. Therefore, there is no change in angular momentum; angular
momentum (L) is conserved.
where I
i
is the initial rotational inertia and
ω
i
is the initial angular speed. The
initial rotational inertia is that of a disk
and the final rotational inertia of the combined disk and ring is
where r
1
and r
2
are the inner and outer radii of the ring.
So the final rotational speed is given by
Equipment Required
ScienceWorkshop
®
750 Interface (CI-
6450 or CI-7599)
Rotary Motion Sensor (CI-6538)
Mini-Rotational Accessory (CI-6691)
Mass and Hangar Set (ME-9348)
Base and Support Rod (ME-9355)
Triple Beam Balance (SE-8723)
Paper clips (for masses <1 g)
Calipers
L
I
i
ω
i
I
f
ω
f
=
=
I
i
1
2
---
M
1
R
2
=
I
f
1
2
---M
1
R
2
1
2
---M
2
r
(
1
2
r
2
2
+
)
+
=
ω
f
M
1
R
2
M
1
R
2
M
2
+
r
1
2
r
2
2
+
--------------------------------------------------------------
ω
i
=