I was given a homeowork where i need to explain why did water cool down slower when it had a coat of oil on top of it. We had a cup with just water and a cup with same amount of water but some oil on top. I know the starting temperatures and the temperatures after 10 min in the cups, i know the volume of water and oil, i know the size of the cups, i know the mass of the mixture. But i don't know how to explain this problem with formulas. I would really like to know where to start, what to calculate. Thank you.
the teacher gave me this problem to solve. So i hope you can help me with it. Here is the problem: John poured 150ml ob boiling water in 2 cups made out of polystyrene. Cups are open on the top so heat goes out there. Temperature of the outside air is 20°C. In 1 cup he add 5 mm thick layer of hot oil. He measured starting temperatures and then he measured temperatures again after 10 min. He measured the mass of water and water+oil before and after 10 min.  Here are the resaults:   -cup 1 (only water)  starting temp: 96°C  finnish temp: 64°C  starting mass: 149.4g  finnish mass: 142.42g  -cup 2(with oil on top)  starting temp.: 96°C  finnish temp.:91°C  starting mass: 164.72g  finnish mass: 164.70g  The surface of the both cups is 0.003 m2  Questions: 1.Why did the water covered with oil cooled down slower that the one with no oil? Show with calculations. 2.Why did John use oil with temperature around 100°C and not oil with room temperature? How would the resaults change if he used room temeprature oil? 3. Which other physical values, which are relevant, can you calculate from this informations? Basiccaly i need the physics behing why does this happen.
Find three Poisson-distributed random variables, pairwise independent but not mutually independent Escaping both forward slash and back slash with sed A worker carries two bags. Each of the bags initially contains N nails. Whenever the worker needs a nail, he takes it from a bag picked at random. At some point the worker picks an empty bag. Find the probability that the other bag contains exactly m nails.  My reasoning:  The desired probability: $C_2^1 \cdot P(|A| = 0\ and\ |B| = m)$, where A, B - sets of nails in each bag. Then we can "divide" this probability (I suppose that I deal with independent events):  $P(|A| = 0\ and\ |B| = m) = P(|A| = 0) \cdot P(|B| = m);$  $P(|A| = 0) = (\frac{1}{2})^N$, where $|A| = |B| = N$ (initial condition).  $P(|B| = m) = (\frac{1}{2})^{N - m}$  Result: $C_2^1 \cdot P(|A| = 0\ and\ |B| = m)$ = $C_2^1 \cdot (\frac{1}{2})^{2N - m}$  Am I wrong or it is correct? I'm searching for applications where the distribution of the eigenvalues of a unitary matrix are important. Example properties of the eigenvalues could be that the eigenvalues are clustered, that they live in some half plane, that, in the case that the matrix is orthogonal, that a certain fraction are 1, etc. When customers buy things from a store, you say:  (1) Customers give ABC Store business.  If I "turn this around", can I say:  (2) ABC Store obtains or acquires business from its customers.  Do these verbs work in (2)? In Clash of Clans there was an update on 9/16 adding a Tie-breaker into the wars, can anybody explain in detail how this mechanism works? Windows says RAM ran out while there is still 4 GB of physical memory available How do I run an executable using Lua? Breadcrumb hyperlink header Add title uniqueness to the heuristics for detecting low-quality questions This feature request is a response to  Two days ago,  suggested that we . However, given that  (hat tip ) as well as ...  262  103   ... I suggest that we take it a step further. Let's extend the heuristics for detecting—and blocking—low-quality questions to enforce unique titles, or at least flag new questions with duplicate titles automatically. We can leave the precise heuristics of detecting a duplicate title up to the Stack Overflow development team. I have no delusions about the fact that a few questions will &quot;slip through the cracks.&quot; The goal here is to be proactive about minimizing the number of duplicates, and I think that the best place to start is the existing heuristics for detecting low-quality questions. After all, duplicate question titles are bad for a number of reasons: They often indicate a question that is itself a duplicate, but perhaps just as importantly, they decrease the signal-to-noise ratio when searching for questions. I honestly can't think of any reason that duplicate question titles are helpful, unless you are asking for a solution to the same problem in a different programming language. Even then, I think that it would be acceptable to rephrase the question to say &quot;How do I do X in (insert programming language here)?&quot;  makes a good point about the potential problems with this solution:  I have a hunch that if we do that, people will find ways to circumvent it (changing case or punctuation, adding random spam), and we'll end up stuck in a an arms race.  We may get stuck in an arms race with some users, but I honestly think that many people new to Stack Overflow just don't understand the etiquette of asking questions here. If we could even convince people to rephrase their question more clearly 20% of the time, I think that it would be a tremendous boon to the community. Furthermore, remember that heuristics for low-quality questions already exist, arms race or no. How can I take a screenshot with Selenium WebDriver? Reasons why not to update an Ubuntu version to a newer/older kernel version How does "proof of effort" make a question better? It seems like many questions by new users are downvoted immediately.  Sometimes there is a comment to the tune of "lacks research", "we're not here to do your homework", or "show us some effort".  Now I wonder, what does it matter how much work someone has done before posting?  If someone can ask a good question in 5 seconds, more power to them.  To illustrate this point, look at how you could "improve" a question to include proof of effort.  You could put in 5 failed code snippets and their in- and output.  This would make for very long questions with a high noise ratio.  Another suggestion is to add "research".  By "research", I suppose most programmers mean "Google".  So this is basically a suggestion to add a list of fruitless Google queries.  That doesn't sound interesting either.  How can "proof of effort" turn a bad question into a good one? How do I change the hostname without a restart? I want to change the OS hostname but I do not want to restart.  I have edited /etc/hostname but it requires a restart to get implemented. How to avoid this? How can I replace a relay with a MOSFET Transistor? I have this working         &ndash; Schematic created using   An Arduino commute both relays and a power adapter charge each battery at a time.  I would like to replace each relay by a MOSFET. How can I do that?  I think the solution bellow will not work because DRAIN is always connected to SOURCE and this will short circuit batteries. MOSFETS only isolate from SOURCE to DRAIN.  When the D9 is HIGH, D10 will be LOW so the power adapter will never be charging both batteries simultaneously.          Sorry for the messy schematic.  Thank you very much. What determines how much experience I get from a hearthstone match in play mode? Sometimes I win handily and get a little experience, sometimes I squeak out a victory and get a lot.  How is experience earned? Trying to install Ubuntu on Dell XPS 15 (9570) I have been trying to install Ubuntu on my new laptop:     Dell XPS 15 (9570)   Windows 10 Home 64bit English   8th Generation Intel(R) Core(TM) i7-8750H Processor (9M Cache, up to 4.1 GHz, 6 cores)   16GB, 2x8GB, DDR4, 2666MHz   256GB M.2 2280 PCIe Solid State Drive   NVIDIA(R) GeForce(R) GTX 1050Ti with 4GB GDDR5     I began by trying to install Ubuntu 18.04 LTS using an 8GB USB drive. The first issue I ran into was getting frozen on the bootup screen on the fourth dot. After a couple tries, I plugged in my monitor (through HDMI) and it stopped getting stuck all of a sudden.    Next, I tried to go through the installation and when I clicked on restart now, my computer froze and I had to shut it down manually and start it back up again. At this point I got to the login screen and logged in but after entering my password it got stuck on a purple screen with my mouse pointer (which was frozen). I was able to get into a shell at this point (with ctrl+alt+f4) and attempted to run sudo apt-get install nvidia-390 but this froze when it reached building initial module for 4.15.0-22-generic and upon reboot I had to run sudo dpkg --remove -a.    I was unable to work around this so I attempted to install Ubuntu 16.04 which I could only do by adding acpi=off to the boot configuration (which by the way, I had a lot of trouble getting to since GRUB usually flashed in and then immediately disappeared and only occasionally would it stick around long enough for me to use). But when I try to boot up now, I never reach the screen with the five dots and instead immediately get stuck on a purple screen (with no mouse pointer).  I reinstalled Ubuntu 18.04 and am back to being stuck on the log-in screen.  What should I do? Was the Wookiee language fully designed or is it just random emotionally-relevant sounds? We know that some of the other Star Wars languages were fairly well developed by the movie's creators, in terms of vocabulary, grammar, etc.  Was the Wookiee language designed in this level of detail or did they just try to put together sounds that made sense emotionally? Error: Declaration of MyClass::start_lvl() should be compatible with that of Walker_Nav_Menu::start_lvl() Is there any way to keep a command from being added to your history? I have a command that I want to keep out of my history file, and I really don't care to have it there when I search the history stored in memory, though that's less of a concern. Is there any way to prevent this, or do I just have to go back and edit my history file.  update: I didn't realize this might be shell-specific. My shell is zsh. You're welcome to answer for other shells so people know how to do this in their shell.