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Layman here.

I'm not sure if this is the case or not, but my anecdotal evidence is that mobile phones, especially large screen phones, tend to fall face down when you drop them; much to the owner's dismay, this leads to cracked screens.

I'm sure there is a scientific explanation for this, so I'd like to know: Why do mobile phones tend to fall and land face first (if so)?

I have a feeling it's related to the way your toast always falls butter side down, or how the shuttlecock always turns toward the same direction, but I'd like to know the explanation.

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    $\begingroup$ It is possible that phones land face up as often as face down, but we remember the face down landings much more easily. $\endgroup$ – Todd Wilcox Nov 9 '17 at 1:08
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    $\begingroup$ There's actually a cat inside each phone: that's how they work. When you drop the phone, the cat flips to land feet first, which is screen-side down. $\endgroup$ – CJ Dennis Nov 9 '17 at 1:53
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    $\begingroup$ Apply butter to the back of your phone to counter this effect. $\endgroup$ – DeepSpace Nov 9 '17 at 8:29
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    $\begingroup$ Or strap the phone to the back of a cat. $\endgroup$ – Barmar Nov 10 '17 at 7:29
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    $\begingroup$ In fact, do both just to be safe. $\endgroup$ – thanby Nov 10 '17 at 13:42
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A physicist working at Motorola actually did this experiment as part of a promotional push for shatter-proof screens. This same physicist had previously written a paper on the same question, applied to the classic "buttered toast" problem (does toast really land butter side down?).

The short answer is: the way the phone lands depends on how it is oriented when it leaves your hand. People tend to hold their phones the same way: face up, at an angle, fingers on either side, slightly below the phone's center of gravity, at just about chest-high. The phone also tends to "fall" the same way: slips out of your hand and you fumble slightly trying to catch it.

Given all those parameters, when the phone drops out of your hand, it typically flips over a half a revolution by the time it contacts ground. If you were holding the phone flat, or upside down, or lower to the ground, the result would be different. But given the relative uniformity of the way people hold the phones, there's a corresponding relative uniformity in the way they land when dropped.

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    $\begingroup$ It'd actually be interesting to investigate this independently of the fall height and path, i.e. depending only on the phone's own shape and mass distribution. $\endgroup$ – Gallifreyan Nov 8 '17 at 22:31
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    $\begingroup$ @davidbak academia.edu/6794263/… $\endgroup$ – Keith McClary Nov 9 '17 at 3:53
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    $\begingroup$ Worth noting that Robert Matthews was actually awarded an Ig Noble Prize for his research: improbable.com/2012/12/24/tumbling-toast-the-maths $\endgroup$ – pajonk Nov 9 '17 at 6:54
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    $\begingroup$ I have no idea anymore where I read the follow-up research, but I recall this being a universal property. Even on other planets with different gravities, bipedal humanoids would have their hands at heights inversely proportional to the gravity, which kept the average number of rotations at 0,5 independent of gravity. $\endgroup$ – MSalters Nov 9 '17 at 9:44
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    $\begingroup$ But also keep in mind that Matthews says in the video that there is "a slight tendency" to land screen down, so you shouldn't place too much emphasis on the physics. $\endgroup$ – WhatRoughBeast Nov 9 '17 at 19:14
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I think one of the commentators summed is up nicely, that you are more likely to forget the times when it lands face up.

It's a psychological phenomenon that Christopher Chabris and Daniel Simons touch on in their book: "The Invisible Gorilla".

In short, it comes down to the fact that a phone falling face-down tends to be much more traumatic for the owner of said phone, and the mental trauma caused tends to leave a bigger impact on your memory. Whereas a phone landing face-up is quickly forgotten. Thinking back, one is therefore likely to only recall the phone falling face-down.

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    $\begingroup$ If you're looking for actual psychological terms to read about, try cognitive bias; in this case confirmation and negativity biases would be a good place to start. $\endgroup$ – nexus_2006 Nov 10 '17 at 13:04
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    $\begingroup$ “The root of all superstition is that men observe when a thing hits, but not when it misses.” -- Francis Bacon $\endgroup$ – user175007 Nov 10 '17 at 14:05
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The answer by @KutuluMike gives a good reason.

Psychology can enter in the way one holds a phone even if not chest high to be given a half rotation. The crux is that the phone always faces out of the palm of the hand. It would be an unusual owner who would have the palm on the screen face, so even from low levels where rotation is not possible the probability of the palm letting go downwards is higher than on edge or back of phone.

Seldom a phone will be ejected from the palm ( falling downstairs?) in a random direction. If the palm faces up, the phone is safe, if down , as it is always held face out hitting with the face down is the most probable outcome.

So ultimately the answer to "why do phones land face down" is "Because they are held in the hand face up."

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    $\begingroup$ I would add that in the time available for the falling object to strike the ground, there is insufficient time for aerodynamic effects to affect the orientation of the phone. this is not true for flat objects dropped from a height of, say, 5 to 10 meters. $\endgroup$ – niels nielsen Nov 9 '17 at 19:26

protected by Qmechanic Nov 9 '17 at 6:35

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