Scale Definition and 743 Threads

Watching the Australian Open and they use a heat stress rating to protect the players. I've searched for the details of how it is calculated without success. Anyone know the formula that they use? Just curious.

Summary:: Strap a weight-measuring bathroom scale to your feet and jump on a trampoline: weight measurements at different points of each jump? What is the longest part of the cycle you are in the free-float frame? I am studying Spacetime Physics 2nd ed. by Taylor and Wheeler at the suggestion...

M F Ice Point 77°M 32°F Steam Point 437°M 212°F 437°M - 77°M = 360°M 212°F - 32°F = 180°F ∴ M = 2F M = 2(68°) M = 136° But this is incorrect. The answer is actually 149°M. Please help.

In cosmology we have a scale factor that depends only on time ##a(t)##. Now how can I solve this thing $$\frac{d}{da}(\dot{a}(t)^{-2}) = ?$$ Is it 0 ? Or something else ?

For A, I had multiplied 65 and 9.8 since that’s the force of gravity. For B, I again multiplied 65 and 2.5 (that’s what the scale says it reads. *I believe you multiply them for c and d, but I’m not positive for it. C- I think you multiply then subtract D- I think you multiply and I’m not sure...

'Imagine that you live in a different universe, which may have a different cosmology to our own. You measure the distances to and redshifts of a large number of Type Ia supernovae, and you use the redshifts to calculate the scale-factor of the universe at the time when the supernova exploded...

If we take a flat universe dominated by radiation, the scale factor is ##a(t)=t^{1/2}## which can be derived from the first Friedmann Equation:$$(\dot a/a)^2 = \frac{8\pi G}{3c^2}\varepsilon(t)-\frac{kc^2}{R_0^2 a(t)^2}$$ But suppose I want to show this using the second Friedmann Equation (Also...

Imagine a Universe where the Hubble parameter is truly a constant, in both space and time. How much smaller would such a Universe be 14 billion years ago compared to today? Using the Hubble parameter in terms of scale factor: ##H(t) = \frac{\dot{a}}{a}## leads to the differential equation...

One of the things I have yet to come across in the explanation for the expansion of the universe is the effect of light... Most all of the matter we observe out there are stars - fusing nuclei and radiating EM energy in incomprehensible quantities... And this has been happening since the dawn...

Hi PF! Fluids in low gravity have a natural oscillation frequency ##\lambda = \sqrt{\sigma / (\rho L^3)}##, where ##\sigma## is surface tension, ##\rho## density, ##L## characteristic length. Then given a particular object, say a sphere, is ##L=D## or ##L=r##? How about a channel; would ##L##...

EDIT: As per @Orodruin 's suggestion(s), I have edited my problems and equations, sorry for the confusion as I typed this out hasty. So from this question, I understand I have to find the net force for the first 10 seconds and deceleration for 20 seconds. The scale shows the force with which...

Summary: How is the universe best viewed considering the great difference between smallest and largets things? I am not sure how to phrase this question so forgive me if it is all wrong. I have noticed that science is doing a lot with small, very small things. They also do a lot with big...

There are 3.35*10^25 molecules in one liter of water. If we are given a penny for every molecule, how high could you stack the pennies given that a stack of 17 pennies equals one inch? Or, to further reduce this large number into something more tangible, how many stacks equal to the distance...

Firstly i worked out the scale factor of the universe R(t)/R(t0) = 1/1+z = 1/1+11.1 = 1/12.1 = 12.1^3 = 1/1772 The distance between the galaxies were 12.1 times less than today and the volume was 1772 times smaller than today. Then I think the average density in the universe at that time is...

My reasoning is that 1)at initial condition, net force of stick on the beaker is equal to the weight of the weight minus the buoyant force applied by the water to the weight, which is the tension force in the string. The recorded weight should be equal to mass of beaker + water + net force of...

According to Sean Carroll's The Cosmological constant(https://arxiv.org/pdf/astro-ph/0004075.pdf) (Eqn.20) cosmological observations imply that the magnitude of the vacuum energy density in natural units is given by $$|\rho^{(obs)}_\Lambda|\le (10^{-12}\ \rm{GeV})^4.$$ Does this imply that the...

Good evening everyone. Can you tell me if it is possible to mathematically derive the Bernoulli principle from a microscopic analysis? In particular, in the hypothesis of an incompressible stationary flow, at a constant altitude, it states that: P + 0.5ρV^2 = cost Well, in textbooks this...

In order to get a very general sense of the scale of order of magnification power of telescopes: If a hobby telescope i have, has a magnification power of X100, what would be the magnification power in terms of X, of the following: 1. Hubble 2. James Webb 3. Gravitational lensing

I wrote the following code in MATLAB: t = [0:0.001:0.1]; noise = randn(1,size(t,2)); a = 15*10^9; b = 15*10^(-3); c = 7*10^8; y = a*exp(-t/b)+c+noise*100000000; fun = @(p,t)p(1)*exp(-t/p(2))+p(3); p0 = [15.5*10^9, 14*10^(-3), 6*10^8]; p = lsqcurvefit(fun, p0, t, y); t_fit = [0:0.0001:0.1]; y_fit...

From the continuity equation ##\frac{\partial \rho}{\partial t}+\rho (\nabla • u)=0## where ##\rho## is the mass density and is homogeneous and ##u## is the velocity of expansion or contraction. For an expanding volume this becomes ##\nabla•u=\frac{\dot v(t)}{v(t)}=\Theta## which gives the rate...

If, as suspected, the Andromeda galaxy "colides" with our own sometime in the far future, would the gravitational forces from passing stars have effect on our solar system? In accelerated models the interaction looks quite violent, but how would it be in our "uncharted backwaters of the...

QS) A model of a bus has a scale of 4cm to 3m. The model is 10cm long. What is the real length of the bus? my workout: 4cm to 3m. 4 cm is length of model and 3m is real length. so we have, mode = 10 cm long so 4 cm to 10 cm: 10/4= 2.5 cm for real length 3 X 2.5= 7.5 m. I am not sure about...

Electronegativity has seen a number of scales throughout its years of existence. Starting from the Pauling scale to the Allen scale, Wikipedia has a long list. Recently, Martin Rahm, Tao Zeng and Roald Hoffmann have defined a new scale for electronegativity. The news has been published in...

Homework Statement A closed funnel is 10 meters above a weighing scale. At t=0 we open the funnel. and 15kg of sand are coming out of it every second. The velocity of the sand when it comes out is 13m/s, directed downwards (towards the scale). At a certain moment the scale displays a value of...

Lately I've been really interested in creating a chatbot that could learn and talk to users. The only problem though that's preventing me from starting is the time it may take for the program to find the data it needs in memory. Most chatbots simply find the closest match to your words and then...

G’day. I am here to clear my doubt about the dB scale, in general, and it’s use in calculating received power in a microwave cavity. Given that I have arrived at received power (Pr in Watts) for a given input power (Pt), I understand that 10*log (Pt/Pr) yields Pr in dB. Now, say, the...

Hi. I've just re-read a high school introduction about SR. It introduces the relativistic mass. I know that this concept isn't used anymore in modern formulations of SR, but observations should be the same in all formulations. They make the following thought experiment: An electric tram and...

Homework Statement Is the least count constant for Vernier scale like 0.1 mm or variables? 2. The attempt at a solution If the main scale readings are 10 mm and the vernier scale readings are 9 mm, the least count is MSD/VSD = 9/10 = 0.9 So the least count is 0.1 mm for every count in the...

hi, I'm designing a 50ftx50ft, 8-cable Cable Driven Parallel Robot and am thinking this is a pivotal decision. the corner posts are 10ft tall and the machine should be able to lift 100lbs at least 5ft off the ground. traveling speed of the end effector is less important than accuracy but I'm not...

Ant-Man can shrink to the subatomic quantum realm where space and time cease to have meaning. Can he reaches inside the Planck scale? I wanted to use the words "below" or "above" the Planck scale. But when describing inside it.. do you use "below" or "above" the Planck scale to describe inside...

This is first post so bear with me. This might be totally a blue sky thought ( ok it almost assuredly is ). But when reading about the frame dragging near black holes I wondered if this effect might also be seen ( at a far lower intensity ) in the motion of galaxies. Not suggesting that...

I currently have a cheap digital scale that will measure, say, from 1 g and beyond to the hundredth place with reasonable accuracy, but for anything less than a gram, it is erratic. For example, when I'm adding 0.15 g of a chemical, sometimes the value will change but often it will not and...

I need to scale my solar system model and it's not working. I'm making an augmented reality app that shows a sample solar system rotating. It works great! (Thanks to this $7 program https://assetstore.unity.com/packages/tools/physics/gravity-and-orbits-solar-system-105300 . The Unity engine...

Am I correct in understanding that locally, ie, with respect to circumscribable phenomena, conservation of energy is valid in the cosmos but that otherwise it is/may not be? Otherwise said, the source of dark energy does/may not obey this principle? Or is this a question that does not fall...

Hey all, This is clearly a very simple question but for some reason my roommate and I just can't agree on this. The scenario is as follows: There is a helicopter sitting on a scale. The helicopter weighs 700kg and thus has 700*g = 6867 N of force acting on it by gravity. In order to fly the...

<Moderator's note: Moved from a homework forum.> 1. Homework Statement I have some summarized Likert scale data from a report and my co-workers want to know what kind of comparison analysis we could do with it. I don't have the raw data. Most of the questions are on a 7-point scale (Strongly...

Would it make sense to ask? Is there any other scale for cosmic collisions? What about supernovae? Google is stupid sometimes.

Hi, I am using Octave to do simulations. I have multiple curves in the same figure. I want to change the scale of y-axis after some point to capture more details. For example, the default y-ticks are 1, 0.8, 0.6, 0.4. 0.2, 0. Between 1 and 0.4 the default scale is good for my curves, but...

Hello! I marked the thread as a basic high school level, because I assume my question is just at that level. ) I am reading some materials on statistics now, and, not having enough background yet, I stumbled upon this sentence: "As an example, 50°C, although five times as large a number as...

Hi, I would like to raise a question about Role of magnetic field while formation of small to medium scale stars emerging from nebula ?

Hi there. I am a novice but I was wondering what you all think is the most applicable mechanical energy storage device for small scale off grid applications is. I just read the thread on pump storage and it seems like a good idea but I thought I would keep it broad. Thanks!

I was wondering about the microscopic reason warm air rises up, while cold air comes down. I am aware of the macroscopic reason - density changes. But what happens microscopically? Decrease in density means that the gas molecules are widely spaced out, but their mass remains the same. Then why...

Homework Statement A galvanometer of coil resistance 50.0 Ω deflects full scale for a current of 3.50 mA. What series resistance should be used with this galvanometer to construct a voltmeter which deflects full scale for 35.0 V Homework Equations /Known Variables[/B] R1 + R2... + Rn = Rtotal...

We can define the relationship between ##z## and ##a(t_e)## as, $$1+z=\frac {a(t_0)=1} {a(t_e)}$$ When we assume ##z=2##, it means that ##a(t_e)=\frac {1} {3}## Is this means that universe was ##\frac {1} {3}## times smaller then now ? If its the case then let's suppose ##z=6## which means...

Homework Statement Homework EquationsThe Attempt at a Solution The option (a) says that the 1st coin remains at its earlier position. Due to gravitational force, the 1st coin falls down, hence option (a) is wrong. I don’t understand the difference between option (B) and (C). In my opinion...

For a school project, I've got to choose a subject. I chose "Emergence", but I have to narrow it down a little bit. So, that's why I'm creating this topic. The definition of emergence that I use: By emergence, I mean the fact that proprieties of one scale implies other proprieties by changing...

Homework Statement A cuboid with a mass of M is put on a weighing scale. First the situation is the one in the picture (the ball doesn't move), the cuboid stays on the cuboid without moving. What will the scale show? Now yarn number 2 is torn, the cuboid still doesn't move. What will the scale...

Homework Statement hello, just came across this type of question for first time. A voltmeter with a range of 0-30volts is to be used to measure a 120 volt circuit. calculate the value of the resistor to be placed in series with the meter. the sensitivity of the meter is 1000 ohms per volt ...

Falaco solitons are unique in their longevity, reportedly up to 15 minutes on the surface of a body of still water. For details and the math see {{ http://www22.pair.com/csdc/pdf/pdf/falsol.pdf }} In addition, this persistence occurs at relatively macroscopic sizes in the range of 10 to 40 cm...

Is it possible that Kelvin and Platinum Temperature Scale give same reading of Temperature?