# Why does the spatula twist when I throw it? **URL:** \ **Category:** Factual Questions\ **Created:** [February 27, 2008, 1:50am UTC](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326 "2008-02-27T01:50:42Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [February 27, 2008, 5:47pm UTC](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326/21 "2008-02-27T17:47:37Z")
Whodathunk this many people had experience flipping hammers? ---
**Author:** ![Dragwyr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dragwyr/32/2855_2.png) [@Dragwyr](https://boards.straightdope.com/u/Dragwyr)\ **Post date:** [February 27, 2008, 5:53pm UTC](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326/22 "2008-02-27T17:53:29Z")
I wasn’t expecting nearly this much attention to this thread. Thank you all for your answers. I will endeavor to explain the answer to my 11 yr old who was scratching his head along with me on this one. ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [February 27, 2008, 6:30pm UTC](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326/23 "2008-02-27T18:30:01Z")
I posted: > [@](#): > > ETA: We’re all talking about claw hammers here, I think. The effect doesn’t happen with a symmetrical hammer. To which **zut** replied: > [@](#): > > And that one’s not true. So I tested it. I have 3 symmetrical hammers. The rubber mallet rotated only once out of 12 tries. The deadblow hammer did not rotate in 12 tries. The two-pound copper hammer was harder to handle than the others, and I dropped it 11 out of 12 tries. I caught it once, by the head. The two-pounder taught me nothing, except about my clumsiness. Please note that I did not grip the hammers like a handshake. To keep my palm from imparting any spin, I held my thumb over the end of the handle. I held my forefinger underneath, a few inches forward. In my past experiments with a claw hammer and the same method, the hammer rotated every time. This reinforces **Mangetout** ’s statement about the face being heavier than the claw. I am not a physicist, though I have a rudimentary understanding of some of the principles. I can’t begin to explain my practical results. You physicists can have a crack at it, if you like, but don’t tell me it’s impossible. ---
**Author:** ![av8rmike](https://avatars.discourse-cdn.com/v4/letter/a/edb3f5/32.png) [@av8rmike](https://boards.straightdope.com/u/av8rmike)\ **Post date:** [February 27, 2008, 7:32pm UTC](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326/24 "2008-02-27T19:32:19Z")
The effect in question is “[Rotational Stability](http://scienceworld.wolfram.com/physics/RotationalStability.html)” and the people who said it’s the _intermediate_ axis that’s unstable are correct. You can see the effect with any rectangular object that is homogenous in mass distribution and sides of three different lengths, e.g. remote control, small piece of wood, a book, etc. And I know people are talking about hammers and spatulas, but the effect is the same, since they all have three mutually perpendicular axes of rotation. If you carefully toss the object such as to cause rotation about only one axis, you’ll see that the object will seem to execute a “flip” in mid-air about one of the axes. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 27, 2008, 7:39pm UTC](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326/25 "2008-02-27T19:39:48Z")
[QUOTE=zut] That’s a misleading statement, if not simply untrue. [/QUOTE] Which part? Elaborate. ---
**Author:** ![zut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zut/32/2875_2.png) [@zut](https://boards.straightdope.com/u/zut)\ **Post date:** [February 27, 2008, 8:00pm UTC](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326/26 "2008-02-27T20:00:57Z")
[QUOTE=AskNott] I am not a physicist, though I have a rudimentary understanding of some of the principles. I can’t begin to explain my practical results. You physicists can have a crack at it, if you like, but don’t tell me it’s impossible. [/QUOTE] Your statement that “the effect doesn’t happen with a symmetrical hammer” is incorrect. Telling you that is not the same thing as telling you it’s impossible to throw a hammer just squarely enough to minimize the perturbation. I’ve done that myself, although not very reliably, with a claw hammer. > [@Mangetout](#): > > Which part? Elaborate. The part about “this is a very good example to help understand the dynamics of the whole thing” coupled with the part about “the hammer head is conspicuously heavier than the claws.” The fact that the head is asymmetric is true, but it doesn’t, by itself, explain the rotational instability. If you thought it did, then your statement is incorrect. If, on the other hand, you meant “the imbalance as it leaves your hand likely leads to a perturbation of the unstable system, causing the twist,” then your statement is true, but misleading, because it could be read to mean the asymmetry is _necessary_. As a demonstration of that, I refer you to **AskNott** ’s post. ---
**Author:** ![GargoyleWB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gargoylewb/32/199_2.png) [@GargoyleWB](https://boards.straightdope.com/u/GargoyleWB)\ **Post date:** [February 27, 2008, 8:06pm UTC](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326/27 "2008-02-27T20:06:57Z")
Flipping remote controls has been a lifelong hobby of mine. After years of practice, I can pretty reliably flip remotes, books, and other similarly shaped items without having the unstable axis flip. It is a great way to win a few bucks at a party by challenging others 🙂 The unstable axis has a very small critical point for forgiveness, after which it becomes exponentially unstable. I suspect it is something like a 3-axis saddle-shaped hyperbolic surface, but I’ve usually had too many drinks to explore the math by the time I start pondering it that deeply. Expert level is to try for n+1 rotations without an axis flip. 2 flips is incredibly difficult, I’m maybe 1:10 doing this if I have my flipping chi flowing, otherwise it’s near impossible. I’ve done 3 once or twice, and it was the cause for great rejoicing and drinking. ---
**Author:** ![zut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zut/32/2875_2.png) [@zut](https://boards.straightdope.com/u/zut)\ **Post date:** [February 27, 2008, 8:17pm UTC](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326/28 "2008-02-27T20:17:43Z")
[QUOTE=av8rmike] The effect in question is “[Rotational Stability](http://scienceworld.wolfram.com/physics/RotationalStability.html)” and the people who said it’s the _intermediate_ axis that’s unstable are correct. You can see the effect with any rectangular object that is homogenous in mass distribution and sides of three different lengths, e.g. remote control, small piece of wood, a book, etc. And I know people are talking about hammers and spatulas, but the effect is the same, since they all have three mutually perpendicular axes of rotation. If you carefully toss the object such as to cause rotation about only one axis, you’ll see that the object will seem to execute a “flip” in mid-air about one of the axes. [/QUOTE] A good example, but a slight nitpick: If you toss the book so that it rotates about the other two principal axes, it remains stable (those axes are the one that runs through from front to back cover, and the one that runs vertically parallel to the spine). As another reference (for those interested): > [@](#): > > Consider the motion of a book thrown into the air.[sup]1[/sup] Books have three main axes. If we idealize a book as a brick with rectangular faces, the three axes are the lines through the centers of opposite faces. Try spinning the book about each axis. The motion of the book spun about the longest and the shortest axis is a simple regular rotation, perhaps with a little wobble depending on how carefully it is thrown. The motion of the book spun about the intermediate axis is qualitatively different: however carefully the book is spun about the intermediate axis, it tumbles. > > [sup]1[/sup][sup][sub]We put a rubber band or string around the book so that it does not open.[/sub][/sup] from [\* Structure and Interpretation of Classical Mechanics\*](http://books.google.com/books?id=H_6Ux04cPv8C&pg=PA113&source=gbs_toc_r&cad=0_0&sig=-J6eDQh7nqFtVM7paFCyC3w4gfk) by Gerald Jay Sussman, Jack Wisdom, and Meinhard Edwin Mayer. ---
**Author:** ![av8rmike](https://avatars.discourse-cdn.com/v4/letter/a/edb3f5/32.png) [@av8rmike](https://boards.straightdope.com/u/av8rmike)\ **Post date:** [February 27, 2008, 8:38pm UTC](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326/29 "2008-02-27T20:38:01Z")
[QUOTE=zut] A good example, but a slight nitpick: If you toss the book so that it rotates about the other two principal axes, it remains stable (those axes are the one that runs through from front to back cover, and the one that runs vertically parallel to the spine). [/QUOTE] I should have phrased it, “If you carefully toss the object such as to cause rotation about _each of the three axes at a time_, you’ll see that the object will seem to execute a ‘flip’ in mid-air about one of the axes. About the other two, it won’t.” ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 27, 2008, 9:43pm UTC](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326/30 "2008-02-27T21:43:20Z")
[QUOTE=zut] Your statement that “the effect doesn’t happen with a symmetrical hammer” is incorrect. Telling you that is not the same thing as telling you it’s impossible to throw a hammer just squarely enough to minimize the perturbation. I’ve done that myself, although not very reliably, with a claw hammer. The part about “this is a very good example to help understand the dynamics of the whole thing” coupled with the part about “the hammer head is conspicuously heavier than the claws.” The fact that the head is asymmetric is true, but it doesn’t, by itself, explain the rotational instability. If you thought it did, then your statement is incorrect. If, on the other hand, you meant “the imbalance as it leaves your hand likely leads to a perturbation of the unstable system, causing the twist,” then your statement is true, but misleading, because it could be read to mean the asymmetry is _necessary_. As a demonstration of that, I refer you to **AskNott** ’s post. [/QUOTE] I did actually think the latter - the conspicuous asymmetry of the hammer head makes perturbation inevitable - and it makes it happen in a predictable fashion. If you flick a hammer with a symmetric head, the effect is haphazard - it doesn’t manifest the same way - or at all - in every instance. [Previous page](https://boards.straightdope.com/t/why-does-the-spatula-twist-when-i-throw-it/439326.md?page=1)