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||<:30%>[:PiraScheme#Mechanics: Table of Mechanics Demonstration]||<:30%>[:MEEquipmentList: List of Mechanics Equipment & Supplies]||<:30%>[:Demonstrations:Lecture Demonstrations]|| ||<30%  style="text-align:center">[[PiraScheme#Mechanics|Table of Mechanics Demonstration]] ||<30%  style="text-align:center">[[MEEquipmentList|List of Mechanics Equipment & Supplies]] ||<30%  style="text-align:center">[[Demonstrations|Lecture Demonstrations]] ||
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'''Topic and Concept:'''

 . Rotational Dynamics, [[RotationalDynamics#ConsrvationAngMomentum|1Q40. Conservation of Angular Momentum]]

'''pira200 Listed'''
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 * '''Cabinet:''' [:MechanicsCabinet:Mechanic (ME)]
 * '''Bay:''' [:MechanicsCabinetBayB9:(B9)]
* '''Cabinet:''' [[MechanicsCabinet|Mechanic (ME)]]
 * '''Bay:''' [[MechanicsCabinetBayB9|(B9)]]
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attachment:RotatingPlatform-01-400.jpg {{attachment:RotatingPlatform03-400.jpg}}
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'''Description:''' '''Abstract:'''
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One stands on a rotating platform and with a set of dumbbell, extend and retract their arms while rotating.

||<:style="width: 60%" :40%>'''Equipment'''||<:30%>'''Location'''||<:25%>'''ID Number'''||		 An instructor or volunteer stands on a rotating platform holding a set of dumbbells. While rotating, he or she extends and retracts his or her arms while rotating causing the angular speed to change.
||<40%  style="&quot; ;text-align:center">'''Equipment''' ||<30%  style="text-align:center">'''Location''' ||<25%  style="text-align:center">'''ID Number''' ||
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||Rotating Platform||ME, Bay B9, Shelf #1|| ||
||Dumbbells||ME, Bay B9, Shelf #9|| ||		 ||Rotating Platform ||[[MechanicsCabinetBayB9|ME, Bay B9, Shelf #1]] || ||
||Dumbbells ||[[MechanicsCabinetBayB9|ME, Bay B9, Shelf #2]] || ||
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'''''Important Setup Notes:'''''
 A. The volunteer may get dizzy from spinning.
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'''Setup:''' '''''Important Setup Notes:'''''

 * Demonstration may require practice.

'''Setup and Procedure:'''
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 1. Level the platform  1. Level the platform using the bubble level in the center of it(see photo) by adjusting the relative heights of the three brass feet.
 1. Have the volunteer carefully step on to the rotating platform.
 1. Hand the volunteer the pair of dumbbells, and have him or her hold one in each hand straight out from his or her sides to make a "T shape".
 1. Make sure it's okay with the volunteer to give him or her a little spin. If it is, then give the volunteer a little push to set him or her spinning. Otherwise, you'll need a new volunteer.
 1. Once spinning, have the volunteer slowly bring his or her arms in close to the center of rotation. The rotational speed will increase.
 1. Have the volunteer extend his or her arms again, and observe that the rotational speed assumes (close to thanks to friction) its original value.
 1. To stop the volunteer, let him or her know that you are going to stop his or her spinning. Do so by gently grabbing his or her shoulders. If this is set up next to the lecture bench, the volunteer can stop alone by grabbing the lecture bench in passing.
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 1. Demonstration may require practice.
 * The volunteer may get dizzy from spinning.
 * The volunteer should be careful in getting on/off the rotating platform.

'''Discussion:'''

 . Once the volunteer is spinning, he or she has some amount of angular momentum which must be conserved. This is given by L = I*ω. When the volunteer brings his or her arms into the center, the moment of inertia I is decreased. Since L is constant, ω must increase, which is what we observe.

|| {{attachment:RotatingPlatform-01-250.jpg}} || {{attachment:3lbBarBells-01-250.jpg}} || {{attachment:RotatingPlatform-02-250.jpg}} ||
|| {{attachment:RotatingPlatform04-250.jpg}} || {{attachment:RotatingPlatform05-250.jpg}} ||
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'''Demonstration:'''  '''Videos:'''
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First have the volunteer step on to the rotating platform and have them try to spin while holding the dumbbells. Have the volunteer now hold the dumbbell horizontally at arms length and give the volunteer a gentle rotation.

While standing with arms extended and rotating on a rotating platform, have the volunteer bring the weight to there chest to help illustrate conservation of angular momentum. If necessary, one can sit on a stool that is placed on the rotating platform as well. The person now rotates faster. To slow down have them just re-extend there arms. Note that only the speed of rotation changes not the direction of rotation like with the bicycle wheel.


||attachment:RotatingPlatform-01-250.jpg||attachment:3lbBarBells-01-250.jpg||attachment:RotatingPlatform-02-250.jpg||
  * [[https://www.youtube.com/user/LectureDemostrations/videos?view=1|Lecture Demonstration's Youtube Channel]]
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 1. List any references  * [[https://en.wikipedia.org/wiki/Angular_momentum|Wikipedia - Angular Momentum]]
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[:Instructional:Home]		 [[Instructional|Home]]

Table of Mechanics Demonstration

List of Mechanics Equipment & Supplies

Lecture Demonstrations

Rotating Platform and Dumbbells, 1Q40.10

Topic and Concept:

pira200 Listed

Location:

RotatingPlatform03-400.jpg

Abstract:

An instructor or volunteer stands on a rotating platform holding a set of dumbbells. While rotating, he or she extends and retracts his or her arms while rotating causing the angular speed to change.

Equipment

Location

ID Number

Rotating Platform

ME, Bay B9, Shelf #1

Dumbbells

ME, Bay B9, Shelf #2

Important Setup Notes:

  • Demonstration may require practice.

Setup and Procedure:

  1. Set Rotating Platform out on the floor.
  2. Level the platform using the bubble level in the center of it(see photo) by adjusting the relative heights of the three brass feet.
  3. Have the volunteer carefully step on to the rotating platform.
  4. Hand the volunteer the pair of dumbbells, and have him or her hold one in each hand straight out from his or her sides to make a "T shape".
  5. Make sure it's okay with the volunteer to give him or her a little spin. If it is, then give the volunteer a little push to set him or her spinning. Otherwise, you'll need a new volunteer.
  6. Once spinning, have the volunteer slowly bring his or her arms in close to the center of rotation. The rotational speed will increase.
  7. Have the volunteer extend his or her arms again, and observe that the rotational speed assumes (close to thanks to friction) its original value.
  8. To stop the volunteer, let him or her know that you are going to stop his or her spinning. Do so by gently grabbing his or her shoulders. If this is set up next to the lecture bench, the volunteer can stop alone by grabbing the lecture bench in passing.

Cautions, Warnings, or Safety Concerns:

  • The volunteer may get dizzy from spinning.
  • The volunteer should be careful in getting on/off the rotating platform.

Discussion:

  • Once the volunteer is spinning, he or she has some amount of angular momentum which must be conserved. This is given by L = I*ω. When the volunteer brings his or her arms into the center, the moment of inertia I is decreased. Since L is constant, ω must increase, which is what we observe.

RotatingPlatform-01-250.jpg

3lbBarBells-01-250.jpg

RotatingPlatform-02-250.jpg

RotatingPlatform04-250.jpg

RotatingPlatform05-250.jpg

Videos:

References:

Home

fw: Rotating_Platform (last edited 2018-07-18 17:22:11 by srnarf)