Is it just me or are people fucking thick?

aureole · Post by **aureole** » Thu Dec 14, 2006 10:49 am 0

gravy wrote:I'm shocked no one has said how many pages long this thread is on this page yet!

...because by the time you get to post, it'll be the next page. Don't you see you thick fucking twat, the the PAGE COUNT is moving at an EQUAL SPEED to the RATE at which PEOPLE are fucking well POSTING. As you post it moves, and then the thread RISES up to the top of the PAGE, powered by HOT AIR.

diablo · Post by **diablo** » Thu Dec 14, 2006 10:57 am 0

aureole wrote:
gravy wrote:I'm shocked no one has said how many pages long this thread is on this page yet!
...because by the time you get to post, it'll be the next page. Don't you see you thick fucking twat, the the PAGE COUNT is moving at an EQUAL SPEED to the RATE at which PEOPLE are fucking well POSTING. As you post it moves, and then the thread RISES up to the top of the PAGE, powered by HOT AIR.

There are nowhere near enough expletives in that post to get our full attention. Chuff-monkey!

tufty · Post by **tufty** » Thu Dec 14, 2006 11:01 am 0

aureole wrote:As you post it moves, and then the thread RISES up to the top of the PAGE, powered by HOT AIR.

What happens if the thread is in a lift powered by pixie arrows, moving down at a rate proportional to the rise rate of the thread?

diablo · Post by **diablo** » Thu Dec 14, 2006 11:02 am 0

tufty wrote:
aureole wrote:As you post it moves, and then the thread RISES up to the top of the PAGE, powered by HOT AIR.
What happens if the thread is in a lift powered by pixie arrows, moving down at a rate proportional to the rise rate of the thread?

Is it in a vacuum?

DaiStation · Post by **DaiStation** » Thu Dec 14, 2006 11:04 am 0

diablo wrote:
tufty wrote:
aureole wrote:As you post it moves, and then the thread RISES up to the top of the PAGE, powered by HOT AIR.
What happens if the thread is in a lift powered by pixie arrows, moving down at a rate proportional to the rise rate of the thread?
Is it in a vacuum?

Dyson or Hoover? It matters.

Bog · Post by **Bog** » Thu Dec 14, 2006 11:30 am 0

aureole wrote:
gravy wrote:I'm shocked no one has said how many pages long this thread is on this page yet!
...because by the time you get to post, it'll be the next page. Don't you see you thick fucking twat, the the PAGE COUNT is moving at an EQUAL SPEED to the RATE at which PEOPLE are fucking well POSTING. As you post it moves, and then the thread RISES up to the top of the PAGE, powered by HOT AIR.

tufty · Post by **tufty** » Thu Dec 14, 2006 2:33 pm 0

DaiStation wrote:Dyson or Hoover? It matters.

"Nothing sucks like Electrolux"

kalmar · Post by **kalmar** » Thu Dec 14, 2006 2:37 pm 0

OMG. Sucking isn't a FORCE. Doesn't education EXIST any more?

RageMatrix · Post by **RageMatrix** » Thu Dec 14, 2006 2:38 pm 0

Is this still going?

fred_zen · Post by **fred_zen** » Thu Dec 14, 2006 2:40 pm 0

Sucking is definitely one of the leading forces at my university (nnngh - my smiley-fingers are twitching).

RageMatrix · Post by **RageMatrix** » Thu Dec 14, 2006 2:43 pm 0

fred_zen wrote:Sucking is definitely one of the leading forces at my university (nnngh - my smiley-fingers are twitching).

Don't. I've been resisting the obvious jokes for half an hour.

kalmar · Post by **kalmar** » Thu Dec 14, 2006 4:56 pm 0

I can't believe nobody has posted in this thread for over an hour.

Come on you bastards, claim it doesn't fly, I dare you.

Mir Nyet · Post by **Mir Nyet** » Thu Dec 14, 2006 4:57 pm 0

kalmar wrote:I can't believe nobody has posted in this thread for over an hour.

Come on you bastards, claim it doesn't fly, I dare you.

If god had ment men to fly, he would not have placed the plane on a bloody threadmill!

disciple · Post by **disciple** » Thu Dec 14, 2006 5:22 pm 0

This is somewhat of a "trick" question. Not because it is phrased in a
deliberately tricky way, but because people tend to have trouble
thinking about the operation of other vehicles apart from cars which
they know so well.

The heart of the confusion is simply these two important facts:
* cars propel themselves by pushing against the ground via friction
* airplanes propel themselves by pushing against the air
If you can let go of how cars operate and think about what an airplane
does, you'll be able to see the problem clearly.

One good way of tackling this problem is to find a good analogy. But
the analogy must be a valid one else you'll just get more confused.
For example, someone posted the analogy of running on a treadmill. Why
is that a bad analogy? Because one runs by pushing against the ground
via friction between their shoe and the ground. This is how a car
propels itself! It is not how an airplane propels itself, by pushing
against the air. Bad analogy.

Let's use this analogy. Instead of looking at the airplane, let's back
up and go into the airport. Suppose you're walking down to your gate
and pulling your carry-on bag behind you. It's a nice new bag with low
friction wheels. No problem! Up ahead you see one of those moving
walkways. You don't see anyone coming, so you decide to do a little
experiment. You go over to the walkway that is moving TOWARDS you and
place your bag on it. Meanwhile, you step off to the side of the
walkway, and still holding on to the handle of your bag, you continue
to walk along. In fact, you intentionally walk along at the same speed
that the moving walkway is going, just in the opposite direction.
Question: does the bag move or does it remain stationary as you keep
walking? Obviously it moves with you. So why does your bag move
forward when you are walking at the same speed of the conveyor going
in the opposite direction?

The answer to that question is also the answer to the
airplane-conveyor question. To complete the analogy, the pull of your
arm is analogous to the force of the airplane engines. The bag's
wheels are analogous to the airplane tires. Do the nice low-friction
wheels on your bag on the conveyor pull against you anymore than they
do when you're just pulling your bag along normally? No, they don't.
They are free-wheeling, after all. Meanwhile, you're pulling the bag
with the same force in both cases. So in both cases, the bag keeps
moving forward. Likewise with the airplane, the pull of the engines
doesn't change nor does the force on the airplane imparted by the
tires change no matter what the ground is doing underneath the tires.
You have the same force imbalance in either case, and since Force =
mass x accceleration, you have the same acceleration. Remember, we are
talking airplane engines which push against the AIR, not the ground.
The acceleration is with respect to the AIR, thus the airplane
develops a speed relative to the air and can eventually take off.

That's a long winded analogy. Here's a quicker solution. Engineers
learn to draw Free Body Diagrams to understand such problems. A FBD is
just a block diagram which illustrates the forces acting upon an
object. The net force can be calculated from all the contributing
forces. If that net force is not zero, the object accelerates in the
direction of that force. Let's draw a FBD now. Represent the airplane
by a simple rectangle (the shape doesn't matter). Indicate the force
of the engines pulling on the plane with a large arrow, labeled "F_e"
with e for engines. What force are the tires imparting to the plane?
Remember, they spin freely except for bearing friction and rolling
friction, which produces forces that are quite tiny compared to the
engines. Represent those forces with a small arrow, labeled F_t where
t means tire. What other forces are operating? There is a drag force
too. But remember this drag force is also small compared to the
propulsion of the engines at least at takeoff speeds. Label that F_d.
Code: Select all
      FREE BODY DIAGRAM

   F_d |----------|          F_e
   <---| Plane    |------------->    
       |----------|
     <-- F_t
So what do we have here? We haven't put numerical quantities on these
forces, but instead have just been talking in terms of large and
small. That's okay for the purposes of this illustration. It's enough
to know that F_e is going to be much greater than F_d + F_t pulling in
the opposite direction. If that's the case, we have an unbalanced
force on the plane. Therefore, it accelerates. And it accelerates with
respect to the AIR, since F_e is produces by the engines pushing
against the air.

To sum up: Yes, the airplane takes off. The motion of the surface
underneath the freely-spinning tires is irrelevant to the acceleration
of the aircraft since the tires cannot impart any force to the
aircraft (aside from the aforementioned very small rolling and bearing
friction).

I hope this discussion has helped somewhat and not muddied the waters any further.

John Strong
Ph.D., biochemical engineering
M.S., chemical engineering
B.S., mechanical engineering

Anyone who disagrees live here :

kalmar · Post by **kalmar** » Thu Dec 14, 2006 5:28 pm 0

PWNED BY TEH SCYNSE!!

See, exactly what we flyboys said.

I think I'll allow myself a smiley, just this once