PASCO ME-9341 INTRODUCTORY ROTATIONAL APPARATUS - Manual (Page 35)

012-03051F Introductory Rotational Apparatus
31
Exp 5 – Rotational Collisions
➂ With a few do-it-yourself accessories, the Introduc-
tory Rotational Apparatus can be used to demon-
strate the conservation of angular momentum as in
the spinning ice skater example. You will need:
1. A piece of U-channel with an inside width of
about 1.2 cm and a length of about 25 cm.
2. A cross-hole spindle as shown in the illustra-
tion below.
3. Equal masses of 100-500 grams that will slide
in the channel (the PASCO masses that come
with the Smart Pulley will work).
4. Double-stick tape, thread.
Drill a 1 cm (3/8"+) hole in the center of the U-channel
and attach the spindle as shown in the illustration
below. Attach the U-channel to the platter with
double-stick tape.
Place masses of 100-500 grams on each side of the
channel, and run a piece of thread down the center hole
and out the sides of the cross-hole spindle. Attach
each end of the thread to a mass. Give the platter a
spin. Pull on the thread to vary the distances of the
masses from the center, obtaining a corresponding
increase or decrease in angular velocity.
Introduction
This lab lets students verify the conservation of
angular momentum. In practice, the graphs that
emerge help students to see that the changes in
rotational speed are not instantaneous. Applications
of this principle abound, such as the decrease in an
engine's speed as the clutch is engaged, or the tempo-
rary slowing down of a phonograph turntable as a new
record drops onto it.
Alternatives
➀ This type of experiment can be used to investigate
the moment of inertia of an object. The calcula-
tions are left to the instructor, but in practice,
rather than dropping disks onto disks, the ring or
the steel bar can be dropped.
➁ A second type of collision can be created using two
rotational apparatuses. Each platter is given an ini-
tial rotational velocity, then the two platters are
butted up against each other as shown below, so
they have a common final rotational velocity. A
rim on one of the disks that permits minimal slip-
ping would help to increase the accuracy of the lab.
ω
1
ω
2
Experiment 5: Alternative Method for Collisions
Weight
ω
U-channel
Main platter
Weight
Thread Spindle
Thread
Close-up of spindle
Experiment 5: Conservation of Momentum
Demonstration