what are you doing ?

[Ray P]

In terms of trajectory, if the barrel were perfectly vertical, the geoid perfectly spherical and the air stationery (i.e. no wind) should the ball end up back in the barrel?

[Ray P]

TBH, all you are doing is making it clear you don't understand my sense of humour.

And perhaps the converse.

Entirely possible. Lot's of people don't seem to get my jokes!

[ed]

Well, I am ignoring drag, so if you are ok with that, .

And as we are ignoring drag, first law means we can ignore any losses so would expect 200 = 200 (ignoring direction change).

Good place to find what’s been forgotten

https://en.wikipedia.org/wiki/Equations ... lling_body

I hadn't completely forgotten about the contents of the last post.

I think I'm out now.......Any more from me and it would be cyclic....

If you return to my first post on the subject you will see that my whole premise was based on drag and I thought that was what you were responding to.
As we are discussing two different but related concepts, there would be no likely concencus or agreement to my original post.

but it has been fun(at least for me...I apologise Ray, it seems my sense of humour may have been too dry as well).

[pre65]

but it has been fun(at least for me.

And me.

[Nick]

In terms of trajectory, if the barrel were perfectly vertical, the geoid perfectly spherical and the air stationery (i.e. no wind) should the ball end up back in the barrel?

Are we assuming a flat earth as well or a rotating one?

[jack]

In terms of trajectory, if the barrel were perfectly vertical, the geoid perfectly spherical and the air stationery (i.e. no wind) should the ball end up back in the barrel?

Are we assuming a flat earth as well or a rotating one?

Being flat and rotating are not mutually exclusive...

The world is a spinning disc as any fule kno...

The barrel is long and the projectile a perfect fit...

[Ray P]

In terms of trajectory, if the barrel were perfectly vertical, the geoid perfectly spherical and the air stationery (i.e. no wind) should the ball end up back in the barrel?

Are we assuming a flat earth as well or a rotating one?

I think a truly spherical geoid will be similar to a flat earth - gosh, next we'll be building our own man-capable potato rockets to prove the Earth really is flat - but I neglected rotation - I guess you need the air to be stationery relative to the rotating geoid?

BTW, this is just for fun - I did my O level physics over 40yrs ago but it's a nice interlude from drafting a vision/plan, which is my priority 'working from home' task for the next few days.

[Nick]

Being flat and rotating are not mutually exclusive...

True, but I assumed that if you believed the earth was flat you would also believe you ere the centre of it, therefore you would be rotating around it at the centre of revolution, therefor there was no effective movement just a rotation around the center axis. (though that does assume the barrel is directly above your pointed head.

guess you need the air to be stationery relative to the rotating geoid

Well even then you would notice the precessing as the earth turned below the projectile assuming the air was not solid. See Coriolis Effect

[ed]

apologies, I said I was out, but one further thought occurred a while back which may have a bearing......

as we are talking about a tennis ball(or a potato for that matter) which is malleable(read squidgy) then the percussive effect of the detonation of the propellant might cause the projectile to momentarily deform, at which point it may well adhere to the sides of the barrel. This deformation might take a finite time to resolve whereby the ejection may well be random. This may lead to indeterminate behaviour.....

just saying

also

I've been looking at world globes recently with a view to enhancing the home teaching thing...and I looked at the wiki entry for latitude and particularly the discussion on geoids....Personally I found the whole thing a tad scary.....harping back to my days involved in the early development of GIS...which was also scary until oracle embraced the concept of blobs.

[Nick]

aharping back to my days involved in the early development of GIS...which was also scary until oracle embraced the concept of blobs.

The closest I got to that was writing a viewer for OSCAR (Ordnance Survey Centre Line of Roads) datasets. It was in windows 3.1 so involved loads of madness paging files in and out of memory.

Oracle blobs, thts a whole another world of pain when it comes to supporting them without using client libraries and talking directly to the socket.

[ed]

blobs.....snigger

OSCAR......I have the vaguest of memories.....I designed the first(I believe anyway) iteration of the comprehensive property index which later evolved/mutated into the national property index/gazetteer which I think I'm right in saying is the cornerstone of all local authorities property/planning indexes(not sure if that has a different plural)....BS7666...ahhhh nostalgia....it originally had a reference to OSCAR.

[Ray P]

I work in Remote Sensing so lots of exposure to GIS stuff - there's some amazing capability available today. We're currently working on machine learning techniques to automatically extract datasets - not me personally, I'm to thick to do that sort of stuff, which is why I'm just the team manager.

[ed]

shame we don't live closer Ray, and a shame we can't go down to the pub.....

I rather think there may be things I'd like to ask you...
For the last 3 or 4 years I've given info to weatherunderground....and weather underground have now decided they won't give any data back, just as I was upsizing to start drawing local atmospheric pressure maps...

retirement(kinda forced) and house arrest have left me pondering all sorts of nefarious time-wasting plans....not least of which involves tracking my vehicles whereabouts on a streetmap and plotting pressure contours on freely available os mapping.....

I should be writing songs and playing the piano etc etc but the mind wanders off in the weirdest directions and the stuff of which life was made of seems to be quite ephemeral at the moment.

[simon]

Anyone dropping in here for the first time would think that lockdown was taking its toll. But no, this is what it's normally like here, and why it's such a great place

[Dave the bass]

What he said ^^^^

I love it when they all talk filthy physics