« Last post by chintan on Today at 13:13:01 »
Can we put a needle completely stationary in space? And waht can prove that it is actually an absolute stationary?
« Last post by Don_1 on Today at 13:06:55 »
As I wrote before, there are far too many variables to come up with an equation which would be meaningful.
While some of these variables would be fixed (according to the trailer construction) others would be set by the load, thus remaining constant for that particular journey while others would remain variable throughout the journey.
Trailer fixed variables would be:
Length of trailer.
Trailer deck to roof height.
Rigid or curtain sides or tilt. Flatbeds would add more variables to the load variables.
Anti underrun design: none, bare bars or enclosed bars. I don't know about the US, but in the EU anti underrun is compulsory.
Number of axles.
With or without rear-steer.
Pneumatic adjustable suspension.
The towing unit would also add variables dependant on its aerodynamics and position of the 5th. wheel, both of which will effect airflow over, under and around the trailer. The height of the 5th. wheel, relative to the rear axles of the trailer would set the trailer attitude variable. However, this attitude variable of the trailer and its height from the road will be further effected by the load distribution.
Next come the load variables:
Total weight of load.
Front - back centre of gravity.
Height of centre of gravity.
While the total weight of the load is easy to determine, The centre of gravity could be extremely difficult, if not nigh on impossible to determine, especially with a mixed freight load. Since the centre of gravity would be one of the most important variables to establish, any error in this factor would render any equation worthless.
If you were to load 23t in Denver and drop off 4t in Laramie, then a further 3t in Casper before continuing to your final destination in Buffalo, your total weight and your centre of gravity will change at each drop off point. Add to that a 2t load from Douglas and a further 4t load from Kaycee and you'll spend more time calculating than driving.
Lastly are the journey variables and these can change from second to second and yard to yard.
Turbulence caused by the lie of the land and even the bow wave of other vehicles.
G force exerted through bends.
One variable here would not only be constantly changing but changing so fast and to such a degree, not to mention totally unpredictable is wind speed. While the wind speed may be fluctuating at +/- 10mph around 40mph, there can always be a 'freak' gust of 60+ mph.
As a professional driver, I'm sure that like me, you know the 'feel' of your truck. You can only use your experience to tell you when conditions are becoming such that you need to slow down and be ready for anything.
« Last post by puppypower on Today at 13:02:25 »
A matter based reference, like the earth and our science tools, by being at the top of an energy plateau (relative to C), will result in seeing affects in space that imply more energy that you think you should have. In the figure below, if we were at the top of this large plateau and can't see the edges, but notice all the water appears to pool in a low spot in the middle, one might assume this point is the place of lowest energy; ground state.
Since there is still potential energy in the water; unseen plateau, if the water used this unseen energy to erode its way over the edge of the plateau, we would notice the ground state in now in motion. The potential behind the movement of the ground state would be called dark energy. You can't see dark energy in the lab, because it is not there.
The need for dark energy should have been expected since if we assume there is no center of the universe and no preferred reference, we cannot close a universal energy balance, since difference references will see different amounts of energy. If we had two planets in relative motion V, one with mass M and the other with mass 2M, depending on who you decide is in motion, we can half or double the total system kinetic energy. Say we assume planet 2M is in motion; double the kinetic energy, but in reality M is has the kinetic energy; half the kinetic energy, we will need 75% dark energy to make this assumption work; not preferred reference. If we assume C is the ground state then all references have one universal ground state, so when the pool of water begins to move, this is accounted for without anything new. The C ground state allows you to look over the edge of the plateau you see the C ground state can provides the energy.
One problem that dark energy creates for GR is if we assume we see dark energy far away, and we assume dark energy is everywhere in the universe, what happens to GR if our solar system is also immersed in dark energy and dark matter but we can't see it in the lab? This would mean that GR is not just equating matter, but is lumping unknown amounts of dark matter and dark energy into matter. Say the earth is immersed in dark energy is the acceleration due to gravity (matter based) more than 9.8m/sec2 since dark energy is countering the impact of matter/gravity. We can't see dark energy in the lab so how do we even adjust GR for the earth?
« Last post by Thebox on Today at 12:57:50 »
Object (A) at ground state has zero velocity v=0.
object (A) at ground state has 9.82m/s of acceleration always, this is true or we would have no weight.
1 second of the Caesium clock is equal to ground state is equal to the weight and acceleration,
a golden constant ratio.
Do we account for this?
φ=(1 second = 9,192, 631,770 cycles of the standard Cs-133 transition=a9.82m/s=(F=ma)=Newtons)
Δφ=σ²(1 second = 9,192, 631,770 cycles of the standard Cs-133 transition=a9.82m/s=(F=ma)=Newtons)
Clock (a) at ground state on earth
clock (b) at ground state on a sister earth 1000000 Ly away
M1=M2 in every detail including rotational speed and mass
Clock (a) is always in the present
clock (b) is always in the present
« Last post by evan_au on Today at 10:51:00 »
Quote from: alancalverd
But how do we know the images are distorted?
A image like this galaxy cluster shows many "undistorted" galaxies - elliptical and spirals. Galaxy Zoo will give even more examples.
However, the long arcs don't look like a regular galaxy, but are interpreted as a distorted view of a distant galaxy, an effect predicted by Einstein's General Relativity. We can confirm that the arc is a single object spectroscopically.
There is a mixture of art and science in trying to generate a mass distribution that would bend the light from a distant galaxy into the observed arc. Most of this mass distribution is attributed to "Dark Matter", since the central galaxy is often visible, but doesn't seem to have enough stars in the right places to bend the light into the observed shape.
Unfortunately, these reverse-engineered maps of matter density don't help us solve the mystery of the composition of Dark Matter.
They certainly cause problems viewing unless you log on. Perhaps that's the idea (plus a bit of useful funding for the site ).
« Last post by evan_au on Today at 08:23:28 »
Many muscles are disabled when we are asleep, perhaps so we don't hurt ourselves or innocent bystanders while we are dreaming.
Some muscles must keep working, like heart and lungs, or we die. A lot of these are smooth muscles, that can operate without conscious control.
Other muscles like the ones that control our eyeballs are quite active during REM sleep - I guess we can't hurt anyone with those.
Perhaps having eyelids shut is a protective mechanism - if our eyes were open, the cornea could dry out, and we could get dust in our eyes. This could lead to irritated & scratched cornea. Better to force our eyelids closed while we are asleep!
Physics, Astronomy & Cosmology / Re: Does the mass of a system depend on its enthalpy or its free energy?« Last post by lightarrow on Today at 08:01:32 »
I was inspired by this response in another thread (I added bold for emphasis for the purposes of my question):
I would say it's neither one nor the other but that it's ΔU, variation of internal energy. If volume and pressure doesn't vary, then it corresponds to ΔH (H = U + PV → ΔH = ΔU + VΔP + PΔV); but in general it's ΔU.
« Last post by Vincent M on Today at 07:22:14 »
Feel free to ask me any questions as I don't know if this is the appropriate place/way to vomit information or talk about my experiences.
Go ahead and share your symptoms and any remedies you've found to help you. Hypotheses are also welcome, but I don't find those as interesting. The only thing I can think of as far as rules is to avoid trying to advertise anything.
« Last post by The God Guy on Today at 07:21:49 »
I am a truck driver in Colorado, USA. I drive through all kinds of conditions but some of the most dangerous are in Wyoming where wind speeds can sometimes hit 50-75 mph (80-120 kph). I have been doggedly pursuing an answer to this same question. I have even written to professors in Physics at a University... but not a single person has answered this seemingly simple question. We know the sail area of a a trailer as above described to be 477 sq. ft.....and the other dimensions she described are accurate. We need to have a formula where we can plug in numbers to evaluate risk/safety. the variables are the tractor/trailer configuration..... the weight of the load...if the center of gravity for the load is low, mid level or high (based on the subjective opinion of the driver.....The speed of travel.....The wind speed at 90 degrees angle of the trailer.....forget about any other angle than perfect perpendicular wind force. If someone would create an application I could use on my phone to plug in these variables....I and many other truckers would pay for it.
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