Purpose

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Purpose

Learn about the basic feature of rotational
inertia, rotational energy, and angular momentum.
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Equivalence of rotational and linear principles
Many properties of rotational motion have a
linear equivalent that you are already familiar
with Linear Motion Rotational
Motion Mass (m) Moment of inertia (I)(
difficulty to rotate) Distance (x) Angle
(Q) Velocity (v) Angular velocity(w) Acceleratio
n (a) Angular acceleration (a) Momentum
(pmv) Angular momentum (LIw) Energy
(KE1/2mv2) Rotational energy (KErot1/2Iw2)
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Many laws of linear motion have also equivalent
laws for Rotational motion Linear Motion
Rotational Motion Newtons second
law F ma t I a Equations of Motion for
constant a or a x(t)x0vot1/2at2 Q(t) Q
0wot1/2 a t2 v(t)voat w(t)woat Conserva
tion of (angular) momentum in a system If Fnet0
then pconst. If tnet0 then Lconst
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• Q1
• Use the word, spoke, in your answer.

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Activity I Rotating Bodies and Conservation of
Energy
Setup As hanging mass drops, the plate starts
to rotate faster and faster. Task Design an
experiment to determine whether total energy is
conserved. Important Take into account all
types of energy you can think of that are
relevant here.
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Activity I Rotating Bodies and Conservation of
Energy

• Smart pulley measures
• its own angular velocity.
• Important
• The rotational velocity of
• the smart pulley is related
• to the rotational velocity of
• the round gray platters but
• not equal to it.
• Tangential velocity
• (pulleys radius)(pulleys angular velocity
  from the computer)
• (disks radius)(disks angular velocity)

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Activity 1 p.146 the last paragraph p.147

• Gravitational potential energymgh
• Rotational energy
• Kinetic energy
• Expected result (energy conservation)
• (Data)
• Initial energy
• Final energy
• (Uncertainty)
• Reason

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Activity II Collision Between Rotating Bodies
Setup Main platter rotates, auxiliary platter is
dropped on top of main platter Task Design an
experiment to determine whether total angular
momentum is conserved. Important You need to
turn the main platter upside down as shown in the
diagram.
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Activity 2

• Initial angular momentum
• Final angular momentum
• Is the angular momentum conserved?
• Evaluate uncertainty.

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Activity III The Spinning Ice Skater
Setup U-channel placed on top of platter.
Movable weights (little carts with wheels) can
be pulled Inwards by a thread. Task Test
conservation of angular Momentum as carts are
pulled in. Hint Threads must be routed
through holes on the side of the spindle and come
out on the top of the spindle, where you can
pull on them upwards.
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Hints

• Q6
• You dont have to do this question.
• Data Studio
• Page 2 of the Data Studio workbook contains
  tables.
• If you have taken data on page 1 and want to see
  them on page 2
• in a table, you need to
• go to page 2
• select one of the 4 tables
• click on the Data tab and select the Run you
  wish to see.

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