I just finished my class on circular acceleration and I learnt that centrifugal force (outward force) is a psuedo force. It doesn't really exist.   Now suppose I am going round in my car or a merry go round or whatever. I feel like a force is pushing me from the center and towards the window of my car which is in the opposite direction from center. Now how this be explained?   I asked this to my teacher but he gave an explanation with inertial reference frame which I didn't really understand.   Pardon my grammatical and spelling mistakes.
Currently in my last year of high school, and I have always been told that  does not exist by my physics teachers. Today my girlfriend in the year below asked me what centrifugal force was, I told her it didn't exist, and then she told me her textbook said it did, and defined it as "The apparent force experienced towards the outside of a circle is the centrifugal force and is due to the mass of the object resisting the inward centripetal acceleration that the object is experiencing". I was pretty shocked to hear this after a few years of being told that it does not exist.  I did some reading and found out all sorts of things about pseudo forces and reference frames. I was wondering if someone could please explain to me what is going on? Is it wrong to say that centrifugal force does not exist?   This has always nagged me a bit as I often wonder that if every force has a reaction force then a centripetal force must have a reaction centrifugal force, but when I asked my teachers about this they told me that centrifugal force does not exist.
Minion Pro, TL2016 and LuaLaTeX When I compile with LuaLaTeX and TL2016 this MWE   \documentclass{article}  \usepackage[no-math]{fontspec} \usepackage{luatex85} \usepackage{shellesc}  \setmainfont{Minion Pro}  \begin{document}  \huge{huge} \textbf{\huge{huge}}  \Huge{Huge} \textbf{\Huge{Huge}}   \end{document}   I have this .pdf.     Any help? With TL2015 all is correct. Thanks Is an apostrophe with a decade (e.g. 1920’s) generally considered “incorrect”? I typically don’t use an apostrophe with plurals in any situation, but I always assumed that the use of an apostrophe in constructions like acronyms:     Forty BA’s were given out to students this year.   or numbers:     Though the greatest period instability occurred during the 1950’s when. . . .   was more or less ok. I would personally use BAs and 1950s here, but I've never thought the apostrophe in this case was necessarily “incorrect”. What say ye? What is the EV scale? I have seen an "EV" (exposure value) scale that's sometimes used to express a camera's exposure settings, or scene brightness. How exactly does this scale work? Rewrite Sharepoint URL (Sharepoint 2013) I'd like to rewrite all my site urls in the way the the user can't figure out the exact name of the the page his viewing. let's say that my site is "www.justarandomsite.com"  and may page is "page.aspx" I' like to have instead of "www.justarandomsite.com/pages/page.aspx" sothing like this: "www.justarandomsite.com/skdhfjksdgfjksdgfjdsgvdjhsgfjdsdsjfgkdsjgfkdsgfjdsgfjkdsg" How do I check if a given string is a legal/valid file name under Windows? I want to include a batch file rename functionality in my application. A user can type a destination filename pattern and (after replacing some wildcards in the pattern) I need to check if it's going to be a legal filename under Windows. I've tried to use regular expression like [a-zA-Z0-9_]+ but it doesn't include many national-specific characters from various languages (e.g. umlauts and so on). What is the best way to do such a check? Get full URL (including querystring) from an apex REST endpoint Some things are easier to implement just by hand (code), but some are easier through WF. It looks like WF can be used to create (almost) any kind of algorithm. So (theoretically) I can do all my logic in WF, but it's probably a bad idea to do it for all projects.  In what situations is it a good idea to use WF and when will it make things harder then they have to be? What are pros and cons/cost of WF vs. coding by hand? What's is the origin of Orbital Angular Momentum of electrons in atoms? Consider the Hydrogen 1s electron. We know that, in the quantum picture, the electron isn't orbiting or rotating at all, rather we simply state that the electron is spread over the entire space with the probability of finding it being maximum a radial distance $R$ (=Bohr radius) away from the nucleus. This helps explain why the electron does not radiate EM radiation while in the atom.  But, with this understanding, I do not understand the source of the orbital angular momentum. Is it intrinsic like the spin? SSH Server stops working after reboot, caused by missing /var/run/sshd Does velocity or acceleration cause time dilation? My laptop is filled with viruses and Windows XP is just becoming impossible to work with.   I've been interested in Ubuntu for a while, so, would I be able to use something like Debian to clear my HDD and OS and then install Ubuntu and start fresh? $2\times2$ matrix $A$ such that $A$ has one independent eigenvector while $A^{2}$ has two independent eigenvectors Looking for the title of a book about alien invasion, mining asteroids and using lasers to defend earth What I remember of this novel/series is that the main character creates solar laser satellites and mines asteroids to create more satellites to defend Earth from aliens. Later on, he uses the hollowed out asteroids as a base and eventually as an armored fortress to repulse the alien fleets. I last remember the main character attempting to hollow out more asteroids to defend and attack the aliens eventually. I want to mount the device /dev/sda3 to the directory /foo/bar/baz. After mounting the directory should have the uid of user johndoe. So I did:  sudo -u johndoe mkdir /foo/bar/baz stat -c %U /foo/bar/baz johndoe   and added the following line to my /etc/fstab:  /dev/sda3 /foo/bar/baz ext4 noexec,noatime,auto,owner,nodev,nosuid,user 0 1   When I do now sudo -u johndoe mount /dev/sda3 the command stat -c %U /foo/bar/baz results in root rather than johndoe. What is the best way to mount this ext4-filesystem with uid johndoe set? `apt update` failed on Debian Linux Attempting to upgrade testing/stretch Debian Linux:  $ sudo apt update  Ign:1 http://dl.google.com/linux/talkplugin/deb stable InRelease Hit:2 http://dl.google.com/linux/talkplugin/deb stable Release                                                                    ... Get:25 http://mirror.vorboss.net/debian unstable/main i386 Packages 2016-03-25-1456.28.pdiff [15.0 kB]              Fetched 686 kB in 7s (89.5 kB/s)                                                                                                                                                         Reading package lists... Done W: gpgv:/var/lib/apt/lists/dl.google.com_linux_talkplugin_deb_dists_stable_Release.gpg: The repository is insufficiently signed by key 4CCA1EAF950CEE4AB83976DCA040830F7FAC5991 (weak digest) W: gpgv:/var/lib/apt/lists/deb.opera.com_opera_dists_stable_InRelease: The repository is insufficiently signed by key 419D0ACF314E8E993F7F92E563F7D4AFF6D61D45 (weak digest) W: Failed to fetch http://dl.google.com/linux/talkplugin/deb/dists/stable/Release  No Hash entry in Release file /var/lib/apt/lists/dl.google.com_linux_talkplugin_deb_dists_stable_Release, which is considered strong enough for security purposes E: Some index files failed to download. They have been ignored, or old ones used instead.  What's wrong? How to fix it? Clean URLs and php extension on nginx I've looked at dozens of other questions and references on the web - and by all my calculations, my setup should work, but it doesn't.  I have nginx installation with php-fpm.  If I try to access a .php file, it runs correctly and I get the correct results.  I got this in my config file:  location ~ \.php$ {     try_files $uri =404;     fastcgi_pass unix:/var/run/php5-fpm.sock;     include fastcgi_params;     fastcgi_param SCRIPT_FILENAME  $document_root$fastcgi_script_name; }   Now, I want to setup my web app so that /somedir/file automatically executes /somdir/file.php while still displaying /somdir/file in the browser's address bar.  So I modified my config to contain the following:  location / {     try_files $uri $uri/ $uri.php?query_string }   This kind of works, that is, the server does access the .php file.  Yet, instead of executing it using the existing location ~ \.php$ block above, it simply spits the php source code as the download into the browser.  If I append the .php manually to the requested URL, then the php is executed.  It feels as if once the server matches try_files to $uri.php, it then does not do another pass at locations to see that what it needs to do with the php files.  I tried putting the php block above and below the location /, but it makes no difference.  How can I get the php to be executed? How do you reset the sa password? I lost the sa password on a machine, and when I log in to the machine directly using an account in the admin group, SQL Server Management Studio will not allow me to log in using Windows authentication.  My plan was to simply log into the server, connect via Windows Authentication, and reset sa to use a new password. Since I cant' connect via Windows Authentication, this won't work.  How else can I reset the sa password? Why use a z test rather than a t test with proportional data? What are metaclasses in Python? In Python, what are metaclasses and what do we use them for? I have sucessfully installed AniMove by activating experimental plugins (yay! thanks gis.stackexchange). But I can't find it in Qgis! Yes I have activated it. Where is it? Is this a common bug? I searched for it the toolbox, I looked up the names of the several single tools based on this  and only found "Kernel Density", which is filed under SAGA. But I don't have SAGA installed (and don't know if I need to?)