trivial trivia

[alpha2]

Hint: It's related to "groundspeed".

[bermudahwin]

24 minutes ago, alpha2 said:

Hint: It's related to "groundspeed".

If it was 100 mph  over 100 miles each way with a 10 mph wind the return journey will be quicker than the outward. The total time 2.02 hrs

If there were no wind each trip would be 1 hr each way totlalling 2.00 hrs.

I think... it was calculation number 50 or 60 and my head hurts.

Harry

 

 

[alpha2]

You got the idea. Basically, you spent LONGER going at a slower groundspeed. You spend a noticeably shorter time going faster. More time at 110 kts groundspeed, less time at 90 kts groundspeed.  

I think I only had one student get it right the first time. It's critical, though, as in airplanes, you don't burn miles per gallon, you burn hours per gallon. "Time in your tanks" was the rule.

Jeff

[bermudahwin]

Loads of wasted paper...

I had the feel of it but the maths eluded me, logically I cannot work out if the time was "made up" or not.

H

[alpha2]

You can only make up the time, if the time spent at the two different groundspeeds were the same, but you spent more time at the slower ground speed to cover the fixed distance, and less time at the higher groundspeed over the same distance. Can't make it up. The students always fell into the "groundspeed vs. airspeed" thing. They always figured if your airspeed was the same, you could make it up. Your groundspeed into the wind was 90kts, (100kt airpspeed, minus the 10kt headwind). Return trip, same 100kt airspeed, but 110kt groundspeed. (100kt airspeed plus 10kt tailwind.)

FYI, your time enroute into wind would be around 1:07, and time back would be around :54.

We aren't even getting into density altitude and True vs. Indicated airspeed. Yeah, ground school is a bitch.

Jeff

[Mjolnir]

so how fast are you really going in relation to earths rotation and universal expansion?

[alpha2]

Universal expansion is unclear, as recently it was discovered that as opposed to the universal expansion slowing, as most thought, it was continuing to accelerate. Big shock, so I won't address that.

However, your "airspeed" will be the same. But, there is Coriolis effect. And the effect of that will be different depending on latitude and direction of flight.

It's not just aviation that's affected by Coriolis. Long distance shooting must take it into consideration. Even over 1000yds the impact point on target will be different if firing position is reversed with target location. (Not much, but still...). The field artillery guys take it into account.

Jeff

[alpha2]

One more thing, there is a reason rocket launches into space are done as close to the equator as possible. Earth rotation gives them a head start for picking up orbital speed.

[bermudahwin]

@alpha2 Dang it to heck I was a minute out, but still don't fully understand why.

@Mjolnir the math is a bit questionable, but Monty Python sang the Galaxy Song, which explained it to me.

 

 

 

[Mjolnir]

32 minutes ago, alpha2 said:

Universal expansion is unclear, as recently it was discovered that as opposed to the universal expansion slowing, as most thought, it was continuing to accelerate. Big shock, so I won't address that.

However, your "airspeed" will be the same. But, there is Coriolis effect. And the effect of that will be different depending on latitude and direction of flight.

It's not just aviation that's affected by Coriolis. Long distance shooting must take it into consideration. Even over 1000yds the impact point on target will be different if firing position is reversed with target location. (Not much, but still...). The field artillery guys take it into account.

Jeff

yep. you just explained  why toilets in Australia flush counterclockwise.

[alpha2]

Ah! the Galaxy Song! "splains" so much about things. Catchy tune. 

Oh, and I rounded the numbers on the times. It's actually close to 1:06.5 outbound, and :54.5 return. The E6B Flight Computer is your friend. (See pic). Commonly referred to as the "whiz-wheel". Back before GPS made such things obsolete. Except for pre-flight planning, of course. WOW,  I keep finding more and more things that say to me, "you are SO obsolete, dude!" First Morse Code, now this. I am dismayed.

I just had an "interesting" half hour trying to explain this to my trophy wife. Ended up using the moving walkways at Denver International Airport as an example.

Better than the hour we spent at the end of the grass runway in Frankenmuth, Michigan, explaining why we always take-off and land into the wind. That one required relating to money in your account in the bank. Starting out with a balance, as opposed to a deficit. THAT she understood! She's all about the money.

Jeff

Edited March 31, 2018 by alpha2

[bermudahwin]

Analogies are how I explain lodsa techie stuff, so fully understand yours.

Thank for the explanations

[Mjolnir]

so this is why a plane can take off from a stationary position on a treadmill?

[Mjolnir]

PS if you can see expansion with a telescope then its an optical illusion. it is contracting. and not the building a house kind.

[alpha2]

12 minutes ago, Mjolnir said:

so this is why a plane can take off from a stationary position on a treadmill?

Oh, no!!! We're not getting into THAT bit again! The all time winner, as I recall, on an aviation forum. (But, it is related the "groundspeed vs. airspeed" thing). And, well, rolling wheels, vs. driven wheels. And, a few other things. Co-efficient of friction had nothing to do with it. (What makes an airplane fly? MONEY!)

And, the expansion was not a direct visualization, it was a visualization of velocity change, via red shift, if you believe in that sort of thing. (Totally unrelated, remember "Red Dwarf", the Brit show?).

Wow, talk about thread creep! Eh?

[bermudahwin]

6 minutes ago, alpha2 said:

Wow, talk about thread creep! Eh?

But its not in Show...

[Mjolnir]

what is the greatest book ever written by  Robert Heinlien?

[Mjolnir]

 

[bermudahwin]

Do I recall Ouroboros/Mjolnir  type plot in Number  of the Beast?

I have difficulty with some of the morality arguments in Time Enough For Love, but liked it

Overall I think I'd go for Stranger in a Strange Land.

H

[Mjolnir]

19 minutes ago, hwinbermuda said:

Do I recall Ouroboros/Mjolnir  type plot in Number  of the Beast?

I have difficulty with some of the morality arguments in Time Enough For Love, but liked it

Overall I think I'd go for Stranger in a Strange Land.

H

heh heh. no answer is the correct answer. Grok?

[bermudahwin]

6 minutes ago, Mjolnir said:

heh heh. no answer is the correct answer. Grok?

Doh!

My only excuse is that its midnight, an I was up early to watch AFL live in Australia, from the UK

I got to the right book though

Sheesh, man, how does your mind work. No that's not the next trivia question.

Edited March 31, 2018 by hwinbermuda

[Mjolnir]

9 minutes ago, hwinbermuda said:

Doh!

My only excuse is that its midnight, an I was up early to watch AFL live in Australia, from the UK

I got to the right book though

Sheesh, man, how does your mind work. No that's not the next trivia question.

you win if you get fredk to give up his answer. Grok?

[bermudahwin]

3 minutes ago, Mjolnir said:

you win if you get fredk to give up his answer. Grok?

Not even gonna try

 

[alpha2]

Heinlein = best book, Grok?

I've read them all again, since I retired in December.  And, all the Sherlock Holms, and a lot of others from the wayback machine.

[fredk]

11 hours ago, alpha2 said:

An airplane flies from point A to point B at 100 knots airspeed. It is flying into a 10 knot headwind. Then, it flies back to point A at 100 knots airspeed, with a 10 knot tailwind. Will it make up the time it lost flying into the headwind, when it returns with the tailwind?

yes , although the air speed is the same, the ground speed is different; going A-B the ground speed is 90 knts, going from B-A the ground speed is 110 knts.

T'was one of the first basic questions at navigators classes  in RAF. Then it got more and more complicated; air pressure at various heights, different cross winds, fuel consumption of a Buccaneer S2B in lbs per minute. Got through it all.

Answer to Viking puzzle later...............maybe

Edited April 1, 2018 by fredk