# Search results

1. ### I Object encapsulation

But its just a mathematical notation that semantically doesn't really describe anything by itself. Or in other words, just saying ##U = \sum{U_i} = 0## doesn't really mean anything before you give the details of each ##U_i##. It is a bit like saying the the universe follows the variational...
2. ### Python Understanding Object Type in Python

In general, "type" to a much wider concept than "class". Put very short you could say "class" corresponds to "custom type", i.e. a type with custom semantics defined by the program as opposed being a built-in type in the language in question with a "fixed" syntax and semantics. In Python3, the...
3. ### Special Relativity Time Dilation/Length Contraction Problem

Assuming he is still busy trying to save his infected colleague within that 5 day limit he must have found a way to do at least 0.9999983 c. No wonder we haven't heard from him - I'm not even sure Physics Forum will work at such large Doppler shifts!
4. ### I Object encapsulation

If you by "object" refer to a real world extended object with all its physical and mechanical characteristic and behaviors and by "single equation" mean to write that up into a single unified meaningful mathematical form, then in general, no. Different physical aspects of real-world objects are...
5. ### I Do you have an example of a truly random phenomenon?

I understood Dales (rhetorical?) question to be about whether or not a (discrete) classical systems allows infinite precise state information or not, or in more practical terms, whether there are finite or infinitely many possible states in an arbitrary small ball around a given reference state?
6. ### I Changing the RPM of a frictionless spinning wheel in a box

For the ideal case with no axial friction and, say, a perfectly rigid wheel your experience is correct. To see this you could perhaps ask yourself what mechanical quantity usually is conserved in cases of no friction and see if this helps you conclude something. This will also explain why the...
7. ### Why are there chips in USB chargers?

I haven't tracked the USB standards in any details, but I would expect the USB charging specification to include capabilities that requires some digital signal processing in addition to act as a power source. The specs themselves are not freely readable, but this short USB charging overview also...
8. ### Time-lapse of the future...

If you are thinking about what the point of the universe is, then apparently the scientists here suggest it could be to allow sufficiently intelligent life an incentive to make a baby universe. Not a bad purpose as purposes come, but as an engineer I foresee this will either require some...
9. ### Some ideas on interstellar space travel

I am still inclined to think that if humans ever is to travel to other star systems it is more likely to happen as "seed ships", i.e. slow moving automated ships that transport "embryonic" humans to be "grown" at the destination only if the automation is able to establish a suitable environment...
10. ### Collection of Lame Jokes

Perhaps that is a reference to the fun fact that the ring finger is hard to move on its own when other fingers are fixed at something? At least that is common entertaining "prank" at parties .. well, childrens birthday parties anyway.
11. ### Knight Rider physics questions

I had similar thoughts initially, but in the video it is mentioned that IED's often are placed by the enemy in such a way that the vehicles are likely to end up in rivers, adding drowning as a significant fatality risk.
12. ### Changing folder icon in desktop.ini via python

For "transparent" handling of the local end-of-line convention when opening a file, text mode, i.e. 'wt' in your case, can be a useful option. In your case the program sounds like its specific for Windows making this less of an issue, but in other cases where the local OS doesn't matter text...
13. ### Why Fathers Get Gray Hair

If its any comfort, you are not the only father exposed to a hair de-toning potential from an awesome aviator daughter. For instance, take this young lady currently attempting to fly solo around the globe at record age: https://flyzolo.com/route/ With several of her legs being 4-5 hours over...
14. ### Knight Rider physics questions

I didn't notice the backwards pointing rockets in the diagram until now, but just assumed the "designers" did the only sensible thing for jumping over an obstacle with rockets, namely to let them point downwards. Duh, forgot we are talking movies. Come to think of it, I recall seing backwards...
15. ### I Do you have an example of a truly random phenomenon?

I mentioned lava lamps and my point still stands, namely that the dynamics of a lava lamp is classical deterministic, whereas the Josephson junctions is not. If we want to search for a "truly random classical system" (however vain we kind of all agree such a search will be) we surely are better...
16. ### I Do you have an example of a truly random phenomenon?

It is an interesting model you describe, but it sounds like there are a lot of details in the statistics that has to work out, at least to understand what the process is. I am also not sure what you mean by "eliminating quantum"? I understand it like you use the two junctions to get a normalized...
17. ### Knight Rider physics questions

Are you thinking due to high accelerations? I imagine that if the rockets on KITT are meant to give it a "boost" upwards (allowing it to fly over obstacles in an parabolic path) and not give it sustained flight for any length of time, the acceleration would be high but burn time low, a bit...
18. ### I Do you have an example of a truly random phenomenon?

How do we know a physical system with a continuous state (e.g. the distance between two particles in the system) is in a state of exactly 2, and not one of the infinitely many other values that lies within an arbitrary small ball around 2?
19. ### I Do you have an example of a truly random phenomenon?

Branches in state space sounds similar to symmetry breaking, and that at least has some literature. As I understand it symmetry breaking in an otherwise symmetric system is only considered to be a result of quantum effects (spontaneous or dynamical symmetry breaking) or, for in case of purely...
20. ### I Do you have an example of a truly random phenomenon?

I guess no one would argue that such a bit stream in principle can have unpredictable bits in the sense that there would be no way for anyone, based on measurements of the state of the initial system, to produce a predicted stream that would stay correlated with the actual stream over time. But...
21. ### I Do you have an example of a truly random phenomenon?

Would "unpredictable events" based on deterministic chaotic motion count as an example of deterministic "true randomness"? For example, is the position of the particle within the Lorenz-attractor, e.g. is it in left or right branch, after a very long time truely random or not. For a practical...
22. ### Where does XML fit in relation to website and webpages?

Which can then be (some, but not arbitrary) HTML. I still think "XLST is one way to convert XML to HTML" is a valid first-order approximation in the context of what the OP asks.
23. ### Where does XML fit in relation to website and webpages?

One relationship between XML and HTML is also XLST, a way to directly convert a XML file into HTML for display for instance. Years ago I used that quite a lot make computer generated output nicely displayable in the browser when opened or viewed. I remember one case with a traffic train...
24. ### I Ejecting Rocket Fuel

I assume you pose these questions in order to "fix" the speed constrained model to somehow match the energy output in the totals even if it doesn't match along the way? If so this approach has the problem that the model will only work if we burn exactly the "planned" amount of fuel. If we only...
25. ### I Ejecting Rocket Fuel

No problem. In the mean time I took some time calculating the total kinetic energy in the CM frame of the continuous rocket. During the burn the speed of the rocket is $$v_r = -v_e \ln r ,$$ where ##r = m_r / m ## is the fraction of the mass left in the rocket. This means the kinetic energy...
26. ### I Ejecting Rocket Fuel

I am not sure what argument you are trying make here bringing forces into it, or the point of your last few posts actually. We all here know how this stuff works and you say you do too so I fail to see why you bring it up. If you prefer to calculate in whatever frame you choose then its fine by...
27. ### I Ejecting Rocket Fuel

As jbriggs444 already mentioned it doesn't really matter which frame you choose, as long as you then stay in that frame for both the pre- and post-ejection momentum and energy equations. But if you for the single-chunk ejection choose to go with the rocket frame (i.e. the frame in which the...
28. ### I Ejecting Rocket Fuel

I am not sure why you want to bring in more than one frame of reference, but I hope we agree that for the process of ejecting a single chunk of mass there is only need for one, namely the frame where the center of mass is at rest. There is actually a ejection mechanism that sensible will cover...
29. ### I Ejecting Rocket Fuel

No, you read it wrong. I wrote the kinetic energy out like I did in terms of ##m_f## and the total (constant) mass ## m = m_f + m_r## to clearly show that it varies quadraticly, and not linearly, in ##m_f## and with the first part (i.e. ## \frac{1}{2} m_f v_e^2 ##) separate because that is the...
30. ### I Ejecting Rocket Fuel

I was referring to the single-chunk equations so there is really only one interesting frame. Before ejection the total mass sits at rest, after ejection the two masses move in opposite directions with some total kinetic energy that, as mentioned, does not vary linearly with the mass of the...