Things you always wanted to know the answer to [Vol. 3]

[The Mad Monk]

gowmonster said:

Driving licence thing.


Each licence holder in England, Scotland and Wales has a unique driver number, which is 16 characters long. The characters are constructed in the following way: 1–5: The first five characters of the surname (padded with 9s if less than 5 characters)

https://www.licencebureau.co.uk/driver-licence-num...

my Driving licence starts GOW99

What is the question that you want to know the answer to?

[Roofless Toothless]

MartG said:

227bhp said:

...stuff...

Again, that is not what you originally asked

And for fks sake, for the final time, atmospheric pressure has fk all to do with delivery of water to your house ! I'm a qualified engineer so I know what I'm talking about ! The only instance where air pressure is used to deliver water is onboard a ship, where having a large mass of water at the top of the ship would cause stability issues, so air pressure is used instead.

I had a spell while younger working on the drilling rigs as a geologist. Most of the time was spent in Venezuela, and we used to get some wild and woolly stuff going on down there in Lake Maracaibo.

On one rig, a beat up old platform towed over from Louisiana, we had a blockage, suspected to be an air lock, in the domestic water system. The tool pusher (boss man) decided to blow the water round the pipes by connecting it up to the pressurised air system. Of which we had two, a relatively low pressure one and an evil high pressure one for drilling purposes. Of course, he decided to go for high pressure, for sts and giggles, I suspect.

We were told not to open any taps so that they could direct the flow around the pipes as desired to clear the blockage. We complied, all except my mate, another British geologist, who had no idea what was going on as he was peacefully sitting on the bog, reading a book and minding his own business.

While it was all pressurised up, he finished the task, and with his pants still round his ankles turned round to flush the bowl. Of course, on rigs just like on ships, the water doesn't come from a cistern, but directly from the main and there is a lever to open the tap and release just enough, but no more, water than you need to do the job. This means the flow is directionally proportional to the pressure in the system.

Unfortunately the high pressure blast he released, on trying to make its way round the channels in the rim of the bowl, proved too much for the ceramic to handle, and the rim exploded all over the place, leaving just a jagged stump where the bowl formerly was, and a very surprised offshore geologist standing there, pants at half mast, covered in st and porcelain.

His plaintive cries led us to the rescue, but he was never the same man again.

[MartG]

Roofless Toothless said:

MartG said:

227bhp said:

...stuff...

Again, that is not what you originally asked

And for fks sake, for the final time, atmospheric pressure has fk all to do with delivery of water to your house ! I'm a qualified engineer so I know what I'm talking about ! The only instance where air pressure is used to deliver water is onboard a ship, where having a large mass of water at the top of the ship would cause stability issues, so air pressure is used instead.

I had a spell while younger working on the drilling rigs as a geologist. Most of the time was spent in Venezuela, and we used to get some wild and woolly stuff going on down there in Lake Maracaibo.

On one rig, a beat up old platform towed over from Louisiana, we had a blockage, suspected to be an air lock, in the domestic water system. The tool pusher (boss man) decided to blow the water round the pipes by connecting it up to the pressurised air system. Of which we had two, a relatively low pressure one and an evil high pressure one for drilling purposes. Of course, he decided to go for high pressure, for sts and giggles, I suspect.

We were told not to open any taps so that they could direct the flow around the pipes as desired to clear the blockage. We complied, all except my mate, another British geologist, who had no idea what was going on as he was peacefully sitting on the bog, reading a book and minding his own business.

While it was all pressurised up, he finished the task, and with his pants still round his ankles turned round to flush the bowl. Of course, on rigs just like on ships, the water doesn't come from a cistern, but directly from the main and there is a lever to open the tap and release just enough, but no more, water than you need to do the job. This means the flow is directionally proportional to the pressure in the system.

Unfortunately the high pressure blast he released, on trying to make its way round the channels in the rim of the bowl, proved too much for the ceramic to handle, and the rim exploded all over the place, leaving just a jagged stump where the bowl formerly was, and a very surprised offshore geologist standing there, pants at half mast, covered in st and porcelain.

His plaintive cries led us to the rescue, but he was never the same man again.

Along similar lines - one containership I served on had a deck halfway up the side of the engine room containing some equipment which regularly leaked water. All was fine until one day the drain got blocked. The watch greaser decided to have a go at unblocking it by poking some wire down it - unaware that at the same time the 3rd Engineer had decided to unblock it by applying a compressed air hose to the bottom of the drainpipe down in the bilges. The poor greaser ended up covered in muck and water, and his hat landed on a steam pipe 30' up 3rd Engineer staggered into the control room barely able to walk he was laughing so hard

[ambuletz]

Right, help needed from those who use amazon.

if they can't deliver to you where do they send your package?

I've got about 6 items but 2 of them are not eligible for 'pass my parcel' (as its food related). I work the rat race mon-fri so won't really be around. where do they put it if you aren't around? ill be fine with them leaving it at my local post office sorting office as i could pick that up on a weekend. but you have no idea before placing an order.

[MartG]

ambuletz said:

Right, help needed from those who use amazon.

if they can't deliver to you where do they send your package?

I've got about 6 items but 2 of them are not eligible for 'pass my parcel' (as its food related). I work the rat race mon-fri so won't really be around. where do they put it if you aren't around? ill be fine with them leaving it at my local post office sorting office as i could pick that up on a weekend. but you have no idea before placing an order.

depends who is actually delivering it - if Royal mail then it'll be taken to the local parcel office or put in your 'safe place' if you have one

[ambuletz]

MartG said:

depends who is actually delivering it - if Royal mail then it'll be taken to the local parcel office or put in your 'safe place' if you have one

It doesn't really say. but I have opted for the free delivery/standard delivery as all of it is over £20. i don't have any 'safe space' specified. i seem to recall the last time i used the free delivery it was done using royal mail, but this was on a video game, so it easily slipped through the letter box.... that's not the case here however.

[Bullett]

Truckosaurus said:

Ayahuasca said:

....Nowadays do they just use their iPhones and whatsapp the secret documents back to base, or do they use a secret special spy app?

One assumes that in this day and age there is no need to actually send a man in to look at Secret Documents, they are copied via the use of computer hackers and any 'secret special spy app' will be sneaked onto the phone or laptop of unsuspecting workers in interesting places (eg. whoever cleans Putin's office) to capture whatever the camera and microphone can pickup as they wander about the building.

On the spying thing. I guess its a lot easier these days to have teams communicating secretly as using apps/headphones/bluetooth is all normal and not suspicious.

Which is also why you are not normally allowed to take mobiles into secure facilities.

[Frimley111R]

gowmonster said:

227bhp said:

If I go to the top of the tallest building I can find in the UK and drop a 100kg anvil off it along with a small glass marble at the same time which would hit the ground first?

good question, how much force does the air resistance push up on the 100kg anvil? this would probably depend on the shape and whether it rotates in fall.

the small marble would in theory not have much air resistance so should hit first.

Surely the anvil as its weight would more than offset the air resistance compared to the marble.

[gowmonster]

The Mad Monk said:

gowmonster said:

Driving licence thing.


Each licence holder in England, Scotland and Wales has a unique driver number, which is 16 characters long. The characters are constructed in the following way: 1–5: The first five characters of the surname (padded with 9s if less than 5 characters)

https://www.licencebureau.co.uk/driver-licence-num...

my Driving licence starts GOW99

What is the question that you want to know the answer to?

was an answer to a question asked a few pages ago.

[MissChief]

Frimley111R said:

gowmonster said:

227bhp said:

If I go to the top of the tallest building I can find in the UK and drop a 100kg anvil off it along with a small glass marble at the same time which would hit the ground first?

good question, how much force does the air resistance push up on the 100kg anvil? this would probably depend on the shape and whether it rotates in fall.

the small marble would in theory not have much air resistance so should hit first.

Surely the anvil as its weight would more than offset the air resistance compared to the marble.

Weight matters not when it comes to gravity. Neither does Mass. It's all about the air resistance baby! Crumple up a piece of paper and leave another flat. Both the same weight yet one will hit the floor a lot faster than the other when released.

https://www.youtube.com/watch?v=5C5_dOEyAfk Shows this, as does This: https://www.youtube.com/watch?v=E43-CfukEgs and is far more modern.

[gowmonster]

yes but an anvil weighs more than a marble, so the one with the least wind resistance is the marble (assuming the anvil is the classic anvil shape) but the one with the more weight is the anvil, so does the weight overcome the air resistance?

[RATATTAK]

gowmonster said:

yes but an anvil weighs more than a marble, so the one with the least wind resistance is the marble (assuming the anvil is the classic anvil shape) but the one with the more weight is the anvil, so does the weight overcome the air resistance?

of course not

[Hugo a Gogo]

MissChief said:

Weight matters not when it comes to gravity. Neither does Mass. It's all about the air resistance baby! Crumple up a piece of paper and leave another flat. Both the same weight yet one will hit the floor a lot faster than the other when released.

So how about a sheet of paper Vs a sheet of thin lead, the same size and shape

[gowmonster]

assuming the paper and the lead don't flex, have the same surface area so therefore same drag, and assuming the lead weighs more, the lead will hit terminal velocity faster therefore hit the ground first.

[Hugo a Gogo]

So a long way of saying that weight does indeed matter

I'd suggest the sheet of paper would reach its own very low terminal velocity way before the heavy lead sheet, which might not even reach before it hits the ground still accelerating

In a vacuum, everything falls at same rate
With air resistance involved, generally the heavier object falls faster

http://www.physicsclassroom.com/class/newtlaws/Les...

[fomb]

lord trumpton said:

The poor souls that went down with the Titanic...

What would have happened to the bodies trapped inside the vessel over time? Would they just deteriorate into nothing?

Would there be skeletons left today?

When a person drowns and falls to the bottom of the ocean animals quickly find the body just like a bear or wolf would in the woods and they eat the flesh exposing the skeleton. In the deep sea, the water is undersaturated in calcium carbonate which is what bones are made of so the skeleton eventually dissolves and disappears leaving behind what the animals won't eat. which is commonly their shoes that were treated in tannic acid and evidently don't taste good.

[RizzoTheRat]

gowmonster said:

assuming the paper and the lead don't flex, have the same surface area so therefore same drag, and assuming the lead weighs more, the lead will hit terminal velocity faster therefore hit the ground first.

The paper will hit terminal velocity sooner, but the terminal velocity for the lead will be higher


Think about 2 objects of the same dimensions but different densities.

There are 2 main forces acting on it, gravity and drag

Acceleration due to gravity is constant so both objects will start falling at the same acceleration, but the force acting on the object is Mass x Acceleration, so the denser one has a greater force

Drag is proportional to Velocity squared x Area x Coefficient of Drag. So as they're both the same shape it's purely related to velocity squared.

An object will reach terminal velocity when the drag is equal to the force due to gravity, which will be therefore be higher for the denser object.

If it was a 200kg anvil and a 200kg cannon ball, the ball would land first due to its lower drag and therefore higher terminal velocity, but for a 200kg anvil and a 5g marble, we'd need to work out the anvil's drag coefficient.

However as I have a cup of coffee on the go...

If it was a 200kg iron cube, it would have a drag coefficient of about 1, and an area of about 0.864m^2

At terminal velocity at standard sea level air density (1.225 kg/m3):

Force = mass x Acc = Cd x Area x (air density x Velocity squared) / 2

F= 200 x 9.81 = 1 x 0.864 x (1.225 x V^2)/2 Therefore terminal velocity is about 60m/s, or about 135 mph.

For a 5g, 1 cm marble

F = 0.005 x 9.81 = 0.5 x 0.00008 x (1.225 x V^2)/2 Therefore terminal velocity is about 45m/s, or about 100 mph

Therefore the cube would hit the ground first, and I would expect an anvil to also be quicker than the marble.

[talksthetorque]

RizzoTheRat said:

The paper will hit terminal velocity sooner, but the terminal velocity for the lead will be higher


Think about 2 objects of the same dimensions but different densities.

There are 2 main forces acting on it, gravity and drag

Acceleration due to gravity is constant so both objects will start falling at the same acceleration, but the force acting on the object is Mass x Acceleration, so the denser one has a greater force

Drag is proportional to Velocity squared x Area x Coefficient of Drag. So as they're both the same shape it's purely related to velocity squared.

An object will reach terminal velocity when the drag is equal to the force due to gravity, which will be therefore be higher for the denser object.

If it was a 200kg anvil and a 200kg cannon ball, the ball would land first due to its lower drag and therefore higher terminal velocity, but for a 200kg anvil and a 5g marble, we'd need to work out the anvil's drag coefficient.

However as I have a cup of coffee on the go...

If it was a 200kg iron cube, it would have a drag coefficient of about 1, and an area of about 0.864m^2

At terminal velocity at standard sea level air density (1.225 kg/m3):

Force = mass x Acc = Cd x Area x (air density x Velocity squared) / 2

F= 200 x 9.81 = 1 x 0.864 x (1.225 x V^2)/2 Therefore terminal velocity is about 60m/s, or about 135 mph.

For a 5g, 1 cm marble

F = 0.005 x 9.81 = 0.5 x 0.00008 x (1.225 x V^2)/2 Therefore terminal velocity is about 45m/s, or about 100 mph

Therefore the cube would hit the ground first, and I would expect an anvil to also be quicker than the marble.

As you can see - no marble in sight.

[AstonZagato]

The BBC did an experiment in the world's largest vacuum chamber to prove that only drag matters - gravity exerts the same force on a feather as a bowling ball.
https://www.youtube.com/watch?v=E43-CfukEgs

[RizzoTheRat]

Ah but that's an artificial vacuum You need a slightly bigger budget to do the experiment properly

https://www.youtube.com/watch?v=oYEgdZ3iEKA