Friday, 13 June 2014 16:34

## D1-55: ROTATING ELASTIC RINGS

• ID Code: D1-55
• Purpose: Demonstrate "centrifugal reaction" and to indicate why the earth is oblate.
• Description:
We have a pair of thin steel rings mounted on a rotating base. The top of the rings is free to slide along its axis, while the bottom is fixed to the rotating base.

Turning the crank causes the elastic rings to rotate about the vertical axis. The rotation mechanism here uses the mechanical advantage of a large cranked wheel driving a smaller pulley to give the rotating rings a very high angular velocity.

##### Engagement Suggestion
Before rotating at high speed, invite students to predict what will happen to the rings when you get it spinning as fast as you can. Will they:
• a) keep their circular shape
• b) flatten at the top and bottom and bulge in the middle
• or c) extend upwards and grow narrower in the middle?
Afterwards, encourage students to relate this to other physical phenomena.
##### Background
As the rings rotate, their form distorts, growing wider around the center and flattening at the top and bottom. Interestingly, this is not due to a true outward force acting on the metal at this point, but is an artifact of its rotating reference frame and the forces acting to keep it moving in a circle. This is often termed a centrifugal reaction or centrifugal force, though it is technically a pseudo-force arising from the reference frame.

This effect is seen in astronomy and geography, as rotating planets, stars, and other bodies take on similarly oblate spheroidal forms.

• Availability: Available
• Loc codes: D1
• #### D1-01 STROBOSCOPE AND FAN

Demonstrates rotational motion using stroboscope Read More

• #### D1-12: ADDITION OF ANGULAR VELOCITIES

Illustrate the complex motion resulting from addition of two angular velocities Read More
• #### D1-21: ANGULAR VELOCITY - OBERBECK CROSS

Measure the angular velocity of a rotating object Read More
• #### D1-30: TRAJECTORY FROM CIRCULAR ORBIT - OVERHEAD PROJECTOR

Show that the instantaneous velocity of an object executing uniform circular motion is tangent to the circle Read More
• #### D1-31: TRAJECTORY FROM SPIRAL

Show that forces are required to create circular motion Read More
• #### D1-32: TRAJECTORY FROM CIRCULAR ORBIT

Show that the instantaneous velocity of an object executing uniform circular motion is tangent to the circle Read More
• #### D1-33 ROTATING MASS ON STRING

Illustrates centripetal force and that instantaneous velocity is tangent to the circular path Read More

• #### D1-35 CENTRIPETAL FORCE - ROTATING MASS

Measures the required centripetal force for an object to move with uniform circular motion Read More
• #### D1-36: AIR TABLE - CENTRIPETAL FORCE

Show that centripetal force varies with angular velocity Read More
• #### D1-37 MUDSLINGER

Illustrates centripetal force and that instantaeous velocity is tangent to the circular path Read More
• #### D1-39: PENNY AND COAT HANGER

Demonstrate centripetal force and centrifugal reaction in a dramatic way Read More
• #### D1-40: CENTRIPETAL FORCE ON ROTATING RUBBER BAND

Demonstrate centripetal force and centrifugal reaction Read More
• #### D1-41 ROTATING WATER BUCKET

Demonstrates centripetal force and centrifugal reaction Read More
• #### D1-42: ROTATING WATER BUCKET WITH SPONGE

Illustrate centripetal force and centrifugal reaction with a trick Read More
• #### D1-43: INERTIAL FORCES - BALLS IN ROTATING JARS

Demonstrate inertial forces in bodies submerged in air and in water Read More
• #### D1-44: ACCELEROMETERS AND FRAMES OF REFERENCE

Demonstrate the direction of the acceleration in both rotational and translational coordinate systems Read More
• #### D1-51 BANKED CURVE MODEL

Aid in explaining banked turns Read More
• #### D1-52: FAIRGROUND ROTOR

Illustrate the application of rotational forces Read More
• #### D1-53 LOOP-THE-LOOP

Demonstrates conservation of energy in a rotating object and centripetal force Read More
• #### D1-55: ROTATING ELASTIC RINGS

Demonstrate "centrifugal reaction" and to indicate why the earth is oblate Read More
• #### D1-61: Rolling versus Sliding

Applies conservation of energy to a rolling object Read More
• #### D1-62: CONSERVATION OF ENERGY IN ROLLING BODY

Demonstrate conversion of gravitational potential energy into translational and rotational kinetic energy Read More
• #### D1-63: MAXWELL PENDULUM - LARGE

Demonstrate transformations between gravitational potential energy and rotational kinetic energy Read More
• #### D1-64: MAXWELL PENDULUM - SMALL

Demonstrate transformations between gravitational potential energy and rotational kinetic energy Read More
• #### D1-65: YO-YO

Illustrate transformation between various forms of energy and to perform yo-yo tricks Read More
• #### D1-81: TRICYCLE

Illustrate a tricky problem in rotational dynamics Read More
• #### D1-82: ROLLING FRICTION

Show the direction of the frictional force when a rolling object is accelerated Read More
• #### D1-83: SPOOL

Illustrate a counterintuitive problem in rotational dynamics Read More
• #### D1-84: SPINNING CYLINDRICAL SHELL

A counterintuitive demonstration of rotational dynamics Read More
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