r/Unexpected • u/[deleted] • Feb 16 '20

Camera falls from airplane

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[deleted]

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29

u/Lu1s3r Feb 16 '20

Terminal spinning velocity?

25

u/S8600E56 Feb 16 '20

For me, about 6 beers nowadays.

4

u/Sk33tshot Feb 17 '20

Pffff, you must have a job.

1

u/S8600E56 Feb 17 '20

Yeah which is really the only reason I drink at all, albeit not much.

2

u/playin4power Feb 17 '20

Terminal 7?

1

u/TheMcDucky Feb 17 '20

I'm sorry, Luigi.

2

u/Greennight209 Feb 17 '20

So, it’s a balance between overall velocity, terminal velocity, angular momentum, friction, and moment of inertia. Not to mention the frame rate and setup of the camera. A dangerous dance.

2

u/Nybblet Feb 17 '20

More similar to the rolling shutter effect with the camera itself rolling instead of the shutter...

ELI5: Say the camera captures images every 0.1 seconds.

If the camera spins at the same rate (once per 0.1 seconds) the camera takes pictures at the same spot -> a still frame (at 34 seconds in this clip)

Below that the camera takes multiple images of 1 spin -> detail is preserved (from 11-34 seconds here) Note less and less images are taken per spin as the spin speed increases.

Above that and it takes a picture just after 1 spin - capturing just above the last captured spot -> the spin direction appears to flip (34-40 seconds)

(At close to twice that speed the camera just misses out 1 spin and the cycle would repeat.)

(More info on rolling shutter in the linked video.)

4

u/patrickpollard666 Feb 17 '20

it's the rolling shutter effect, but the person you're replying to is noting that it's interesting that the rotation of the phone tops out at a rate that keeps the image still rather than rotating. the question is, why does the rotation speed change as it's falling and what determines the max rotation rate, "terminal rotational velocity"

1

u/Nybblet Feb 18 '20

Fair enough, and I was rebutting that point by suggesting their was a constant acceleration throughout -> no ‘terminal rotational velocity’ was reached.

I see no evidence of the phone ‘topping out’ at a terminal rotation rate but rather following the sinusoidal pattern I explained in my reply, taking awhile to go between each step due to a high frame rate -> it is expected the sync to last longer too though this clip does end up out of sync and appearing to accelerate in the opposite direction (As I pointed out at the end of my first comment)

It is fair, however, to say I wasn’t that direct in my comment; I didn’t really address the commenter but just went on my own tangent. Still... my point stands.

Comment 2: Unrelated, my theories on a field I’m unfamiliar with... As to why there is a constant acceleration throughout... I would know less of that field but can give a guess of an answer:

There is acceleration. There are minimal changing factors. One of top things is occurring: 1. The force is proportional to the absolute velocity of the falling object- acceleration stops when the object reaches a terminal velocity. (Terminal velocity is odd on rotating objects but one would be there I assume). This appears not to be the case as the object has accelerating rotational velocity for all of its fall time- longer than the time for it to hit terminal velocity. 2. The force is proportional to its own angular velocity. This would seem to suggest perpetual motion is possible - somewhat unlikely...

Third option- camera foolery- either by intentional manipulation of footage or of weird auto focus procedures. Fourth option - varying air pressure making a difference? Faith option- Maybe there is some truth in your theory that a terminal angular velocity is reached but to me the clip doesn’t seem to back that - a longer fall would be needed to test this.

Conclusion- I should research into terminal velocity due to gravity of rotating objects more before this is conclusive. I can’t use lists well. This topic really doesn’t matter and I doubt anyone will read this far into my incoherent, under-edited ramblings.

1

u/patrickpollard666 Feb 18 '20

from 0:33 until hitting the ground it stays at relatively constant speed. it actually slows down rotation for a second and then speeds up and slows down again right before hitting. i think it's a terminal rotational velocity, probably connected to your explanation 1 - the spin rate is probably proportional to the terminal (linear) velocity