Classical Physics

Excuse my complete ignorance, but I'm new to this. I have a question from a GCSE physics book as follows;"Cobalt-60 is a radioisotope made by placing cobalt in a nuclear reactor. It has a half-life of 5 years. The activity of a piece of Cobalt-60 is 32.0 kBq. How long would it take to fall to (a)16.0kBq (b)1.0 kBq?"I guess question (a) would be five years, or one half-life; but what maths/ formulae should I use to calculate (b)? Of course I guess I can get it by just counting down multiplying by 0.5 each time, but I wondered if there's an algebraic formula I should use for this? (kBq is kilo-bequerels) cheerz GIAN

The question is this: At wind proling radar located at 35S is used to obtain measurements of the horizontal winds directly above the radar site. The wind velocity at 1 km is measured to be 5 ms-1 towards the North while at 3 km the wind is 5 ms-1 towards the South. A radio-sonde launched from a nearby location measures the temperature at 1 km to be 7C. Assume the wind is purely Geostrophic and the density of air at this altitude is 1.20 kg m-3. (b) Determine the value of the horizontal pressure gradient at 1km? However, I thought you need two points to find the horizontal pressure gradient? How can I find it at one point? These questions I h…

It seems that some thermoelectric effects (such as Seebeck and Peltier effects) can be associated with carriers (electrons and holes) generation and recombination. But thermoelectric effects can be observed in many metals as well, not only in semiconductors. Can there be such effects as carrier generation and recombination in metals? It doesn't seem to be possible as all electrons in metals are typically free electrons even at 0 K, at elevated temperatures all the more so. How then could there be an electron-hole recombination in metals? For example in Bismuth, Antimony, etc.?

Apologies if I have that wrong. [the SSSC I mean] 25 or so years ago, there were plans afoot, in fact I think construction had already begun, of what was to be known as the Stanford, Superconducting Super Collider. It was then shelved/scrapped for obviously short sighted reasons. my questions, [1] How much more powerful and bigger then the LHC was this going to be? [2] How much further down the standard particle model road would we now be if it was completed to operational standards? [3] Could/would it be possible for construction to begin again? Why not make it an international concern if costs were/was the issue?

Here is a video about 'free energy' and I want to know wether this is some new discovery or can it be explained with current theories of magnetism and electricity:

Hello everyone, Thanks for approval in this forum. My question concerns the cutting of metals. Whether by gas cutting torch or thermal lance, all manufacturers recommend using oxygen with a purity of about 99.5%. They also specify that the performance of the cutting will decrease by about 25% per missing percentage and they place the limit at which it is no longer possible to cut around 95% oxygen. I recently did tests with ultra-thermal electrodes (models that are used under water but which works on the same principle as the conventional 3 m oxygen lance) and I still managed to cut on the surface with a mixture oxy / nitrogen 70%. Hence my questi…

length contraction and magnetic force.pdfMagnetism is intimately related to special relativity. Maxwell's equations are invariant under a Lorentz transformation; the electromagnetic wave equation gives the speed of light c. Many have explained magnetic force as a consequence of relativistic length contraction, for example Richard Feynman in page 13-8 of his ≪The Feynman Lectures on Physics, Volume II≫ and Steve Adams in page 266 in his ≪Relativity: An Introduction to Spacetime Physic≫. If magnetic force is really created by relativistic length contraction, we should be able to derive the expression for magnetic force from the length contraction formula. And indeed we can,…

Doesn't it seem controversial, or t least odd to say that an object of zero mass moves at c. To then turn around and say that to move an object you have to give it mass in the form of energy? The thoughts seems backwards? Maybe it is the scale that seems backwards? Its like saying less is more, unless you want more, then you have to add more. Does moving the object give it some negative value on a scale I am not considering? Is it because an object of zero mass is completely at odds with something that has mass to the point that they are so different that my sudden late night thought is like comparing space to a light particle then saying that because space…

Apparently when one leg round kicks another leg in a shin guard, if a leg is to break it is the kicking leg. See this video from 4:37 to see what i mean - but not if you're squeamish, lots of nasty leg breaks. I'm assuming that factors like bone density aren't a major factor as these are all highly trained athletes. I'm also thinking about the lower leg as a single pole rather than the two bones it actually is, just to keep it simple. So why would the moving poll break upon impact with the static pole and not vice versa? I can only imagine it has something to do with the momentum contained in the distal end of the pole, above the contact point, which means ther…

hi everyone. i have a question in regards to a product im prototyping. i need a solid durable material that will heat up fast and retain heat at the same temperature for 1 minute. does anyone have any good ideas? thanks for your time

Someone told me that energy which a battery can deliver is approximately proportional to a difference in Fermi energy between anode and cathode. I guess it may not relate to metal-air fuel cells because Fermi energy is applicable more to a metals than gases. Fermi energy is also known as an electrochemical potential. So, if we look at Fermi energy table for pure metals, then there is a substantial difference in Fermi energies between Aluminum (11.7 eV) and Sodium (3.24 eV). http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/fermi.html#c1 If we will make a battery with aluminum cathode and sodium anode (or contra) how much energy will it deliver? It is also …

https://phys.org/news/2018-05-subatomic-particle-mechanical-property-reveals.html First measurement of subatomic particle's mechanical property reveals distribution of pressure inside proton May 16, 2018, Thomas Jefferson National Accelerator Facility: "Nuclear physicists have found that the proton's building blocks, the quarks, are subjected to a pressure of 100 decillion Pascal (1035) near the center of a proton, which is about 10 times greater than the pressure in the heart of a neutron star. Credit: DOE's Jefferson Lab" Inside every proton in every atom in the universe is a pressure cooker environment that surpasses the atom-crushing heart of a neu…

Something is really bothering me about magnetic field. So I know we use magnetic field lines to represent the intensity of the magnetic field. For example, the closer they are the stronger the field. However when we look at iron filing aligning in a magnetic field, we see them grouping into distinct lines, almost imitating field lines, but this must mean that the field is weaker between the lines and stronger on the field lines, which makes no sense to me. Can someone explain why the filings form distinct lines and why there are gaps with no filings in them?

I am interested in the mechanics of rigid body rotation. I entered the subject very deeply, and from my calculations and conclusions it follows that, not everything is exactly that haw it is written in books and few details have hidden in present science . Of course, these are my conclusions and should be verified but no one did not get interested, and physicists are afraid of the subject, like the devil of holy water. I thought I might find people here with whom I could discuss the issue, but because the questions for I am looking answers can not be found in books, they only hear excuses. Unfortunately, the local community is just waiting for easy questions which…

Hi! I have a question within thermodynamics. I'll give three different scenarios. 1) Air temperature is higher than the sea temperature. Example: Sea water is 15 degrees, air temperature is 25 degrees. 2) Air temperature is lower than the sea temperature. Example: Sea water is 15 degrees, air temperature is 10 degrees. 3) Air temperature is the same as sea water temperature. How will the air temperature right above the sea water be affected by the sea water in these scenarios. I am interested in the temperature differences at surface, and up to around 70 cm above the surface. The reason I am wondering, is because I am writing a paper on the cool…

i have one idea of resonating wave energy harvesting. i need help on its practical reality. i would like to harvest energy from small packets vibrating on same time as seen in the video (will produce same frewuency in a beed like manner a floating cap at the top will produce the pressure it will transfer downward of the water like beeds.each beed(here bottle) will connected seperately will move at the same time of sea wave.) will produce a high resonating frequency like marching of soldiers on a bridge.

Well this thread title sucks, sorry. I have a plano convex lens (actually equivalent stack of two fresnels each with focal length 120mm, groove pitch: 0.3mm). If I put a photo behind it at a 45mm distance and view through the lens from a 21mm distane, I get perfect focus in the middle area. I am able to correct the spherical distortion by adding a pre-distortion to the original printed photo in photoshop. Similarly I can reduce the chromtic aberration in a similar way. What I can't do is get things on the edges in focus as well. The lens is flexible and bendable. So is the material the photo is printed on. What kind of geometic distortion…

I've been working on something and I need to calculate how much mass I could put on the 10cm thick concrete ceiling of a 5x5 m^2 room before it collapses. I'm pretty stuck on it, tried many things, but none worked. Any ideas?

So here's a clip from The legend of Zelda: Twilight princess How heavy is the goron being thrown, assuming His weight is average rock density, and the radius of his curled up form is approximately 8ft. I tried multiple time to use the sphere volume formula to figure it out, but my latest attempt yielded only 380 lbs. That can't be right. Also, it might be fun to calculate the forces being applied to links body during the throw, once we know how much he's throwing.

I have asked this question, but the topic was pulled to a different side which is human color perception. Because of this reason, I did not get a satisfactory answer. I want to ask again the same question more clearly ,taking refuge in your understanding. Thanks in advance. If we think about all possible color hues according to "Lab Color Space" (lightness values)L* and these colors are saturated ( pure hues without lighter shades ), yellow is the second lightest color next to white and it is also the closest color to white. ( I mean here the lightness, not brightness. If we are talking about the brightness, lime green is perceived by human eye as a brighter color th…

If we think about all possible color hues and these colors are saturated ( pure hues without lighter shades ), yellow is the second lightest color next to white and it is also the closest color to white. ( I mean here the lightness, not brightness. If we are talking about the brightness, lime green is perceived by human eye as a brighter color than white, because our cones are most sensitive at the 550 nm wavelength.) How can this situation be explained physically ?

This may seem like a basic question but, why do all cultures agree on the same units of time, months, hours, seconds, years, while no society can decide on units like torque, pressure, heat and distance. I understand our time scale is based off of the earth's orbit around the sun (year) and its rotation (day) but never understood why all people just accept this unit, especially when we will be a multi-planetary species. Even metric has its issues with Gram-force centimeters vs Newton meters for torque. Or perhaps pressure with Pascal, atmospheres, Torr, psi, inches of Mercury, Gram-force per square meter, etc. To the whole scientific community: please, please, j…

It has been said that if an observer is in a state of acceleration, he can use physics to know it & determine the acceleration. For example, if you were born on a spaceship going to a distant star, and if this spaceship is accelerating say 1g, the young astronaut, after reading books of physics, can make experiments that will tell him that he is in a state of acceleration. He will also be capable to determine the direction of acceleration. Say that the astronaut is indeed measuring that he is accelerated. The value is 1g. He immediately understands that he is traveling aboard a spaceship, accelerating. Now the strange thing is that the direction of the …

Can someone explain how these are mathematically the same?

Is there any material that if applied to or used as a film and illuminated by IR, UV beam or visible light beam or beam of specific polarization will become transparent or opaque in that spot and the opposite when not, and transition at fast rates (<= 8 ms)? Ordinary photochromic films are quite slow with 15 second transition to one state and several minutes to the other.