J.C.MacSwell

Not much call for..?! -- it's the single most popular cheese in the world!

Not much of a cheese shop, here at SFN.

I have a thermos that can keep coffee hot for 24 hours. If you consider the Earth's properties as a thermos, it doesn't seem all that surprising. A vast nuclear reactor surrounded by molten and compressed solid rock twenty times as hot as my coffee, with a volume to surface area ratio millions of times as high (volume increases with cube of radius, surface area with square), surrounded by 20 mile thick skin of solid rock, surrounded by a solar-heated atmosphere, surrounded by vacuum. Not really surprising that we're talking about a timeline of billions of years.

Cue the four Yorkshiremen from Monty Python:

"U'm amazed it's cooled as much as it 'as. Thought it would be tough living with all the heat."

"Never thought it would 'ave cooled enough to have evolved as far as we 'ave. Thought it would 'ave been still too bloody hot."

"Didn't 'spect to even start evolving at all...yet"...Not even an amoeba would try to survive at the temperature I expected it would be."

"What I meant by "living" was more like a pre-amoeba stage. I thought I might be that, perhaps living out on some trans Neptunian object. I certainly didn't 'spect to be evolving anywhere close to Earth."

"I expected to be singed to death on my trans Neptunian object...'alf an 'our before I even tried to form some DNA."...

 

I bet the moon is artificial, full of monitoring equipment and powerfull relay thingummies. Put there by some higher authority to monitor us and to help us evolve. Kinda like in the space odyssey movies.

This is a Science Forum. It has long been proven that it is made of cheese.

Now given enough cheese in one place in space and it will tend toward round due to gravity. Not enough cheese and it stays in a nice tasty wedge shape.

1. Solar radiation

2. Radioactive decay

3. Initial Heat lost at current rate

Not sure if I have them in the right order for the present conditions.

Why not?

 

 

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inertia

Why would the flow lag behind? The force of the flow will be directly proportional to the tension on the rope.

 

The flow would be increasing at that point. It cannot instantaneously adjust to match any change in pressure.

Force is proportional to acceleration, not velocity.

Hey, CP, I'm not ignoring you. I hadn't had time to work out details, so I wasn't sure by inspection if there was an exponent problem or not.

 

The solution to a harmonic oscillator is that [math]\theta=sin\omega t[/math], (for small angles) and the tension will be the centripetal force, which is [math]ml({\frac{d\theta}{dt}})^2[/math], so you end up with a force (and thus pressure) that depends on the square of the trig function. Combine this with the flow rate being dependent on the square root of the pressure, and we're back to averaging cosine and getting 1/2.

 

BUT: the actual results are going to depend on the initial conditions, because you will get slower draining at the peak and faster at the bottom of the path, so it matters where you start the experiment. If you start draining at the minimum level, but with the pendulum in motion (you start it swinging and pull a plug when it's at the lowest point), it will drain slightly faster than if it starts draining at the maximum amplitude.

 

It's not completely certain that YT's discrepancy is statistically significant (~6% is a small difference for 5 trials) and if it is, whether it's due to deviations from ideal motion (e.g. sloshing) or from the solution for large angles being slightly different than the small-angle case. But I think the period increases for increasing angle, which means there should be more time spent at the lower flow rate, which is opposite of the observed effect.

Isn't the period constant for an ideal pendulum?

I don't think that's right. I'm thinking the tension would be greatest at the bottom of the swing, and so would the flow. If you think about it, if the pendulum swung up to a full 90 degrees, the tension (and flow) would be zero at that point, as both bucket and water would be in freefall.

That should be correct, for the tension. The flow would lag somewhat behind.

But that doesn't change the fact that there is no horizontal component adding to the tension at that point in the swing. The tension is all vertical at that point.The tension at that point is greatest there because the centripetal acceleration is greatest at that point.

Would it? The bucket and water have the same acceleration due to gravity. If the line were not taught, no water would leak out at all, so the additional pressure is dependent on the tension, which is varying sinusoidally in time.

 

The time-average of sine oscillating between 0 and 1 is 1/2. It's possible (I haven't actually worked it out) that the effects cancel, and the buckets take the same amount of time (to within one period of oscillation) to empty.

My guess (haven't worked it out either) is that the vertical component cancels out exactly, and because there is an additional horizontal component to the force, always adding to the tension except when the bucket is at the bottom of it's swing, then it would, on average, have more tension and therefore empty faster.

I don't want a complex answer involving fluid mechanics. So assume no sloshing about. Assume that the rate of flow of water out is proportional to the acceleration inline with the pendulum. Assume the bucket is small so the centre of gravity is close to the hole in the bucket.

If it is proportional to the force, it would be faster for the swinging pendulum, since on average the vertical force will be the same, and there are additional components to the force in that case.

Add to CP's remarks, how does the water move, or slosh, relative to the bucket?

It is unlikely to be as regular or in sync with the pendulum swing, so it is quite a complex problem.

If you swung it in a circle at 45 degrees it should empty faster, but that would not be the same thing.

Lift is by definition at right angles to the overall flow (not the orientation of the blade or wing, though they are often close to the same)

The direction of the flow can be relative to the turbine, or relative to the blade, in which case it would change direction from hub to tip, so there is probably a convention of taking it as relative to the turbine as a whole unless otherwise stated.

Drag is in the direction of the flow, at right angles to lift.

You can get a turbine to turn with drag alone, usually with the axis of rotation at right angles to the flow, almost always vertical, but they are generally less efficient.

Note: if you squeeze a pea (pip) it will take off much faster than you squeezed it.

Hi Guys.

 

I'm newly joined, this forum looks great!

 

I was reading through some exam papers from the state exams here in Ireland, and one of the questions was:

 

 

 

I have to admit I'm curious and have been told there are numerous ways - can't think of any after two or three weeks. I know, that's pathetic!

 

Any ideas?

 

Warm Regards,

Ed.

Can you use a known weight and a fulcrum point?

In 1985-86 years I made a number of discoveries and several hundred inventions in the field of savings and production of super-cheap alternative energy. About hundred inventions I even patented or made a patent application.

.

Can you provide a link to one of the more promising ones that you patented?

Or did you only patent the wrong ones?

You may have heard that there are many stories on the internet about adding some magnets somewhere in your engine to make it run more efficient. On most scientific forums and websites, these stories were put in the category of hoaxes, nonsense and such.

 

I recently found an article which seems to come from a more reputable source: Philedelphia's Temple university. They too claim that an electric field will significantly increase the fuel efficiency of the car (a diesel Mercedes), because the viscosity of the fuel is reduced in the electric field. This in turn makes the fuel injection more efficient.

 

I'm not convinced, mostly because I don't understand how it's supposed to work.

 

I have 2 questions for you all:

 

1. How can combustion become more efficient (by as much as 20%) when the exhaust of a car engine is already very low on uncombusted materials? (I have little data on the combustion efficiency of a standard car). I always thought that the main loss of efficiency came from the fact that so little of the combustion energy is turned into motion, rather than incomplete combustion. I have a strong feeling that kinetics of the combustion play a role here, but I'm not sure how those kinetics interact with the rest of the system.

 

2. How does an electric field influence viscosity? Is that because molecules try to line up? Does that then also influence the density? And why would it work with a non-polar fuel such as diesel? Surely, a linear hydrocarbon doesn't care much about an electric field? The chemical composition of diesel is 75% alkanes (paraffins) and 25% aromatic components. None of these are very polar.

It does seem like a credible source.

But for the reasons you mention it sounds implausible unless it somehow improved the timing of the combustion as well, where the timing was off. (grasping at straws here)

Really. Why?

cause

also be

I thought the smallest black holes would be the type to appear in the Large Hadron Collider?

 

 

How did you arrive at the conclusion that it's possible to tow a black hole?

If I dropped you in space and you extended (threw) a rope toward a black hole you would be "towing" it until the rope broke.

Unfortunately it would be towing you as well, in the opposite direction, only faster (assuming you are not more massive than the black hole).

Rope or no rope, by the time you enter the black hole and become part of it you will have displaced it from it's original path.

Correct me if I'm wrong but light curves as it is affected by gravity and therefore undergoes constant velocity acceleration (maintains c while changing direction)

So what is the smallest possible radius of that curvature?

how would I do it using their technology?

 

simple, you use sand/rocks and build it up so you`re always working at Ground level, then when you`ve put all the top parts on, you take away the sand and rocks to leave your structure.

 

Hardly Rocket Science!

But it is "Rock it" science!

This is kinda relavent - You can see/hear the 'time delay' effect with sound rather than light in a thunder storm. If lightening strikes 3 miles a way you SEE it instantly (more or less) but there is a 3 second delay before you hear it crack as thunder. If it strikes 10 miles away then you get a 10 second gap. Similarly, as explained above, light from the sun takes about 8 second to reach us across the 93 million miles it travels.

More like 500 seconds.

valid point, lets say 1kw and 25000rpm

Even a light touch will put it through in that case...

...so you need the speed as well.

Also note that the force will not be directly in the line of travel and there will be a torque as well.

Can you do an experiment?

It wouldn't be a spiral, but it would be curved, and your hole would have to be dug such that it misses the center. (Assuming that it isn't dug from pole to pole)

The moon would still throw you off course.

Where does your iron piping lead to? Are you heating water in it? Where does the fan blow the warmed air to?

 

I would also recommend checking all door and window seals. Open your dishwasher and oven promptly after you use them to let that heat dissipate into the kitchen (dryer too). Change your furnace filters at least every month during winter. Reverse your ceiling fans so warm air is recirculated more efficiently. Buy an insulation wrap for your hot water heater if you don't already have one.

 

I know someone who used an old stand mirror in his back yard to bring sunshine to parts of his yard where the sun couldn't reach, and I wonder if you could do something like this to angle more sunlight into your windows. You'd have to make sure as the day progresses that you're not fading any furniture or pictures.

What's the rush? The heat will dissipate into the rest of the kitchen eventually.

Bernoulli's principle is not a law of physics like conservation of energy. Bernoulli's principle derives from conservation of energy assuming an inviscid fluid undergoing laminar flow at low Mach numbers.

 

The flow around an inverted wing is anything but inviscid or laminar. Conservation of energy does of course apply, but Bernoulli's principle is an improper expression of conservation of energy for inverted flight. In inverted flight, it is the bottom of the wing that does the bulk of work in diverting the airflow downward. Bernoulli's principle is approximately correct for normal subsonic flight when it is the upper surface of the wing that does most of the work in diverting the airflow downward.

 

Even for normal flight, Bernoulli's principle is to me but a hand wave: It begs the question as to why airflow is faster along the upper surface of the wing. By the time you get to a valid explanation for this effect (e.g., via the Coanda effect, the Kutta condition, onset of turbulence), you have already arrived at the fact that a wing diverts airflow downward.

I agree with what you are saying overall but generally it is when the wing is in stall that the lower part of the wing provides most of the lift. This is true whether the wing is inverted or not, and while a non symmetric airfoil will stall sooner when inverted there is no reason the top of the wing cannot provide the majority of the lift for inverted flight.

http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html

 

With all respect, you aren't addressing the question. You are proposing instead that black holes are not the singularities they've been accepted as being. But you have no data for that. What we need is how Bojowald addresses the issue. If he doesn't, then that is a problem with his hypothesis.

 

If he simply stated that it wasn't a singularity, how would that change any of the observable or predictable aspects of a black hole?