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

[talksthetorque]

Vipers said:

How, and to whom do I make a constructive comment to the mods on here to do with the layout?

A Mod, earlier today, with the contents of the suggestion box.

[SpeckledJim]

Ayahuasca said:

Dr Jekyll said:

Ayahuasca said:

How is the speed of sound in air affected by the wind?

Say a plane is flying at 90% of the speed of sound, and it gets a tailwind that pushes it faster, so that its ground speed is well over Mach 1, is it considered to have broken the sound barrier?

No.

Mach is about speed through the air.

Okaaay, so consider a plane flying at Mach 0.9 with a 100 kt tailwind.

How much faster does B have to fly to reach Mach 1?

Mach 0.1.

"tailwind" makes some sense from the perspective of an observer on the ground.

It doesn't make any sense to an aeroplane moving forward through the air in terms of the speed it is doing relative to that air. Flying with a 'tailwind' just means you're moving over the ground faster than you're moving through the air.

[Dr Jekyll]

SpeckledJim said:

Mach 0.1.

"tailwind" makes some sense from the perspective of an observer on the ground.

It doesn't make any sense to an aeroplane moving forward through the air in terms of the speed it is doing relative to that air. Flying with a 'tailwind' just means you're moving over the ground faster than you're moving through the air.

+1

Think of it as the ground sliding backwards, nothing to do with the aircraft or it's behaviour.

Edited by Dr Jekyll on Wednesday 15th November 05:29

[Ayahuasca]

Will a machine be developed that breaks the sound barrier.... under water ?

The speed of sound in water is about 4 times faster than in air, but water is about 800 times denser. So you need something that travels about 2,800 mph underwater. If it could be done, would the sonic boom kill all the fish?

[Einion Yrth]

Ayahuasca said:

Will a machine be developed that breaks the sound barrier.... under water ?

The speed of sound in water is about 4 times faster than in air, but water is about 800 times denser. So you need something that travels about 2,800 mph underwater. If it could be done, would the sonic boom kill all the fish?

Doubtful. I can think of no law of physics that would prevent it, but it would be hugely difficult and expensive, and why would you bother?

[Ayahuasca]

Einion Yrth said:

Ayahuasca said:

Will a machine be developed that breaks the sound barrier.... under water ?

The speed of sound in water is about 4 times faster than in air, but water is about 800 times denser. So you need something that travels about 2,800 mph underwater. If it could be done, would the sonic boom kill all the fish?

Doubtful. I can think of no law of physics that would prevent it, but it would be hugely difficult and expensive, and why would you bother?

Because it hasn't been done yet. The sound barrier has been broken on land, to no practical purpose either.

[Roofless Toothless]

Some of those evil looking buggers on David Attenboroughs program the other night moved at an incredible speed to catch some poor unsuspecting victim wandering past their hole.

I wonder if instantly, over a very small distance, they approach the sound barrier?

[Ayahuasca]

Roofless Toothless said:

Some of those evil looking buggers on David Attenboroughs program the other night moved at an incredible speed to catch some poor unsuspecting victim wandering past their hole.

I wonder if instantly, over a very small distance, they approach the sound barrier?

Maybe. The average person can hold a bit of cord and get the end of it to break the sound barrier and create a sonic boom using nothing more than the power in his/her wrist. A creature that has evolved over millions of years to move fast over a short distance might be able to break the sound barrier too. Maybe a shark with a laser?

[SpeckledJim]

I think the speed of the Mantis Shrimp punch is the fastest animal movement, and apparently that's 12-23 metres per second, so about 10% the speed of sound (on land).

[glazbagun]

Some torpedoes/undersea missiles use supercavitation to reduce friction (they basically turn the water into a gas as they pass through) but I don't think even they top 200mph given the things they need to hunt.

What about the blast wave of a nuke? Does it overtake its own sound underwater? I suppose boiling the ocean gives it a head start.

[JuniorD]

Is this lad



The same as this lad




5001 posts. Woo Hoo.

[anonymous-user]

If you’re swimming in the sea (or a pool) and lightning strikes the water nearby, how close do you have to be to not be electrocuted? Presumably the electricity travels a greater distance on the surface than it goes down in depth? How deep does the electricity typically go?

If you’re in a typical 25 m pool would everything in the pool be electrocuted?

[Johnspex]

If you and a mate are on Pointless, when the subject is announced and you know lots and your mate knows nothing, do you choose to go first or second?

[Newc]

Johnspex said:

If you and a mate are on Pointless, when the subject is announced and you know lots and your mate knows nothing, do you choose to go first or second?

Second. If he bombed out, your better knowledge should reduce your risk on looking for a low score answer.

[Johnspex]

Newc said:

Second. If he bombed out, your better knowledge should reduce your risk on looking for a low score answer.

But if you went first wouldn't it mean you might not be so reliant on him.

Edited by Johnspex on Wednesday 15th November 07:48

[Johnspex]

JuniorD said:

Is this lad



The same as this lad




5001 posts. Woo Hoo.

It makes you wonder why the woman and the older man are taking no notice of the younger man's hands on the woman's throat, and why is the girl watching with that blank look.

[andy_s]

SpeckledJim said:

I think the speed of the Mantis Shrimp punch is the fastest animal movement, and apparently that's 12-23 metres per second, so about 10% the speed of sound (on land).

Pistol Shrimps; microcavitation, temps hot as the sun, sonoluminescence - http://www.bbc.com/earth/story/20160129-the-shrimp...

[Shakermaker]

Johnspex said:

Newc said:

Second. If he bombed out, your better knowledge should reduce your risk on looking for a low score answer.

But if you went first wouldn't it mean you might not be so reliant on him.

Edited by Johnspex on Wednesday 15th November 07:48

It would also depend if you are just giving out "free" answers where there are hundreds of possibilities, or if it is one of those rounds where you have a list of 7 answers to pick from that doesn't get recycled for the next group. But, you don't know that before the round starts.

I think I would go second as well - hoping that nobody else knows the obscure answers that I want to give on a topic as well.

[Moonhawk]

Johnspex said:

It makes you wonder why the woman and the older man are taking no notice of the younger man's hands on the woman's throat, and why is the girl watching with that blank look.

It's probably just one of a number of shots. Sometimes studio photographers take many shots in rapid succession - and whilst one shot on it's own, out of context can look weird - if you saw the sequence, you'd probably see the subjects are just fooling around.

It's the same process whereby tabloids always chose a photo of somebody famous getting out of a car looking completely blotto with their eyelids part closed - when in fact they could be completely sober. The photographer has had their camera on burst mode and simply caught the person mid-blink. If you saw the sequence of photos either side of the one chosen - all you'd see is somebody getting out of a car.......but people just getting out of cars don't make good tabloid stories

[SpeckledJim]

Johnspex said:

Newc said:

Second. If he bombed out, your better knowledge should reduce your risk on looking for a low score answer.

But if you went first wouldn't it mean you might not be so reliant on him.

Edited by Johnspex on Wednesday 15th November 07:48

I would think you'd put the divvy first, as the earlier he goes in the round, the smaller the chance of his pants answer getting taken by another team, and leaving him with nothing.