Work done by frictional force when rolling without slipping
How can friction do no work in case of pure rolling?
Restoring original Settings Menu in QGIS customization? Making some tests in Windows XP for customizing a user interface in QGIS 1.8 (see ), I have unchecked, among other options, the Settings Menu. This means that, after restarting QGIS, there's no way of recovering the older settings because there is not already a Setting Menu. So, I cannot reload any ini file.  For your information, as a precaution, previously I have saved in a folder both the original ini file, with all the options, and the customized ini file with only some options (of course, not included here the necessary Settings Menu).  Before reinstalling QGIS (version 1,8), I would like to try other smarter options if there's any. Where and what does QGIS look at where this applications starts? Period character used for local computer name I'm wondering about the period character . used as a shortcut for the local computer name.  You can use it when logging into Windows 7, for example, to specify that the user account you're entering belongs to the local computer rather than to a domain:  .\MyLocalUserAccount   And you can use it within a Windows Management Instrumentation (WMI) query to indicate that the target is the local computer rather than a remote computer.  You can also use it when working with named pipes to for similar purposes.  However, you cannot use it as the UNC network name for the computer, like this:  \\.\MyShare   Does this character have an official name (e.g. "LocalHostToken") and when and where can it be used for this purpose? When editing a question on , I observed that a link which was not rendered in the post was hyperlinked in the edit preview (see pictures below). I tried reproducing it in the  to see if this also happens when the post is posted for the first time and observed the same. It seems to be a bug after the shift to CommonMark, leading to the different rendering of links on client and server-side. A link following a special character (without any space) is not hyperlinked in the post but is hyperlinked in the preview. A link separated from the special character with a white space appears to have no such problem. (see pictures below and my ). Link not hyperlinked in post  Same link hyperlinked in preview import Excel sheets by name How to avoid becoming stressed while playing endurance games? Although I am asking for Super Hexagon, I've noticed there is a multitude of games (rhythm games in particular) where the more stressed I am, the worse I play and/or are more likely to make a mistake. Often then the games are designed in such a way to induce stress, such as various ways of telling me how far I am, which also is telling me just how much it would suck if I were to fail right now.  This leads to a stress cycle, where I am noticing I am stressed, and I am aware of this being a bad thing, which makes me more stressed, over and around until I eventually fail.  This often means that I probably could've done &lt;some new level I just unlocked&gt; just fine, except I saw that it was new, got stressed about it and started the stress cycle.  So how can I:   Avoid getting stressed while playing Defuse the stress cycle once it has inevitably started   One thought I had for this is simply taking deep breaths, but particularly in Super Hexagon, there is no way to pause and taking deep breaths is distracting enough to make me fail. Is every solution of Einstein field equations unique? Einstein's equation is  $$8 \pi T_{ab} = G_{ab},$$  where the left side contains the stress-energy tensor and the right side contains the Einstein tensor.  Is there exactly one unique stress-energy tensor corresponding to a given spacetime curvature? Or is it possible for one curvature (i.e. one spacetime metric) to be produced by multiple different mass configurations? Follow up: instance control in Java without enum Showing two ring homomorphisms that agree on the integers must agree on the rationals I have two ring homomorphisms $f,g\colon \mathbb{Q}\to X$. I know that $f=g$ on the integers. How can I show that $f$ and $g$ agree on the rationals?   My attempt:  let $x,y \in \mathbb{Z}$, $y\neq 0$.  $$\begin{align*} f(x/y)&amp;=f(x)f(1/y) &amp;&amp;\text{because }f\text{ is a ring homomorphism}\\  &amp;=g(x)f(1/y) &amp;&amp;\text{because }f\text{ and }g\text{ agree on the integers} \end{align*}$$  I do not know how to rewrite $f(1/y)$ so that I can replace it with $g(1/y)$. Any hints will be much appreciated. Thanks. What's wrong with this division? I think there's a lot for me to learn about data types. Why this happens  double result = ((3/8)*100).ToString();   it gives zero .. should be 37,5 ... :( How to prove $ \prod_{d|n} d= n^{\frac{\tau (n)}{2}}$ Google Maps choose zoom to fit country TIGHTLY in given window How did Rita know she lost the power? In Edge of Tomorrow, Emily Blunt's character, Rita Vrataski, had the time-resetting power previously.  She details the backstory of how she gained it, and how she lost it.  However, how did she know when she lost the power?  It's only triggered when the wielder dies.  Obviously she didn't die after losing the power, so how did she know the power was gone? Browse for Servers does not display local instance After Google Play Service update to version 13 I got an error Prove $(1+a+b)(1+b+c)(1+c+a)\ge 9(ab+bc+ca)$ How one can prove the following.  Let $a$, $b$ and $c$ be non-negative real numbers. Then the inequality holds:  $(1+a+b)(1+b+c)(1+c+a)\ge9(ab+bc+ca).$  WLOG one can assume that $0\le a\le b\le c$.  It is not difficult to prove the statement when $0\le a\le b\le c\le 1$ or $1\le a\le b\le c$. Is the sum and difference of two irrationals always irrational? If $x$ and $y$ are irrational, is $x + y$ irrational? Is $x - y$ irrational? Area 51 reputation changes do not show up in the new Top Bar How to make an image center (vertically & horizontally) inside a bigger div Cannot Edit Python Script tool using its context menu from ArcMap/ArcCatalog? I am unable to edit scripts in ArcMap or ArcCatalog.  I navigate to the script, right-click on it and select "Edit", then nothing happens. I am using notepad++ as my editor (set in geoprocessing options). I have looked into this issue () and have attempted the steps therein. However I am still getting the same result, nothing happens.  I am using ArcGIS for Desktop Basic Version 10.3.1 and Python 2.6  What steps should I attempt to solve this issue? I have started a long process through a terminal. Is it possible to make the Ubuntu terminal make a sound once the process is complete? This way, I don’t need to keep checking, but will instead be notified through a sound.