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Rattleback

PRODUCT TYPE: Demonstration

A rattleback is a type of spinning top that prefers to spin in one direction due to its unique semi-ellipsoidal shape.

When spun in the wrong direction, it will automatically shift momentum until it spins in the opposite direction. This is caused by an asymmetric mass distribution and the instability between the rotational axes. As the mass shifts, the rolling axis compensates in the other direction, which in turn causes the mass to shift more.

This continues until the top is spinning in the preferred direction. But when spun in the “right” direction, the mass needs no compensation.

Challenge a know-it-all to explain the physics behind these simple shapes.

 

Dimensions: 3 ⅞" x ¾" x ½" 

$2.50

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Rattleback

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FURTHER RESEARCH
DEMONSTRATION VIDEO
CUSTOMER REVIEWS
FURTHER RESEARCH
RATTLEBACK

A rattleback is a semi-ellipsoidal top which will rotate on its axis in a preferred direction. If spun in the opposite direction, it becomes unstable, "rattles" to a stop and reverses its spin to the preferred direction. This spin-reversal appears to violate the law of the conservation of angular momentum. Moreover, for most rattlebacks the motion will happen when the rattleback is spun in one direction, but not when spun in the other. Some exceptional rattlebacks will reverse when spun in either direction. This makes the rattleback a physical curiosity that has excited human imagination since prehistoric times.

The spin-reversal motion follows from the growth of instabilities on the other rotation axes, that are rolling (on the main axis) and pitching (on the crosswise axis). File:Spoon Celt.webm Rattleback made with spoon exhibiting multiple spin reversals. Original video and idea by Prof. Christian Ucke. When there is an asymmetry in the mass distribution with respect to the plane formed by the pitching and the vertical axes, a coupling of these two instabilities arises; one can imagine how the asymmetry in mass will deviate the rattleback when pitching, which will create some rolling. The amplified mode will differ depending on the spin direction, which explains the rattleback's asymmetrical behavior. Depending on whether it is rather a pitching or rolling instability that dominates, the growth rate will be very high or quite low.

This explains why, due to friction, most rattlebacks appear to exhibit spin-reversal motion only when spun in the pitching-unstable direction, also known as the strong reversal direction. When the rattleback is spun in the "stable direction", also known as the weak reversal direction, friction and damping often slow the rattleback to a stop before the rolling instability has time to fully build. Some rattlebacks, however, exhibit "unstable behavior" when spun in either direction, and incur several successive spin reversals per spin.

DEMONSTRATION VIDEO
CUSTOMER REVIEWS

Customer Reviews

Based on 24 reviews
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B.B.

Very cool toy! I got it for my nephew but we quickly found out our cat likes it, too. XD It also looks neat in the sunlight, as it's translucent.

A
A.S. (Virginia, United States)

Amanda gave this item 5 stars

R
R.P. (Virginia, United States)

This is a cool physics display but didn't meet my expectations. My grandaughter and my son like to make it spin. I thought it would spin more after it stopped and went the wrong way. But the price was good. And we all learned a little bit.

A
A.P. (Virginia, United States)

Andrea gave this item 5 stars

A
A.P. (Virginia, United States)

Andrea gave this item 5 stars

A
A.P. (Virginia, United States)

Andrea gave this item 5 stars

K
K.B. (Virginia, United States)

Such a fun Christmas stocking stuffer! My 11 year old will enjoy playing with this.

K
K.L. (Virginia, United States)

Stocking stuffer for inquisitive kid.

F
F.P.

Great items and wonderful packaging. I will definitely shop from this seller again! Thank you so much!

A
A.M. (Missouri, United States)
Quick shipping

Item was just as described, extremely quick shipping. Will definitely buy from here again.

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Rattleback

Rattleback

$2.50
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