Gravity assisting
Where does the extra kinetic energy come from in a gravitational slingshot?
Home button broken and Notification Center stuck my home button on my ipod touch 5th Gen has been broken for  while so I have been using assistive touch. Earlier on my notification centre got stuck half way down the lock screen, making my ipod completely unusable.   I tried turning it off but the notification centre is blocking the slider and obviously I can't restart it since my home button is broken. Has anyone got any solutions? It's an absolute nightmare! Why would a partition be in use by the system if it isn't mounted? I've been migrating my system from btrfs to ext4 after running into performance issues with VMs. I have two hard drives in my laptop to work with. I've successfully moved my home partition, but the same steps I used aren't working for root.  Progress so far:  I've dd'd my root partition from /dev/sda3 into /dev/sdb3. I modified /etc/fstab to the following:  $ cat /etc/fstab #  # /etc/fstab: static file system information # # &lt;file system&gt; &lt;dir&gt;   &lt;type&gt;  &lt;options&gt;       &lt;dump&gt;  &lt;pass&gt; # UUID=95f13c34-96ca-49e3-bcb2-ff594df31506 /dev/sdb3               /               btrfs           rw,noatime,ssd,space_cache,discard      0 0  # UUID=0fe04f59-599f-41e2-ac30-2ad0f17a9727 /dev/sda2               /boot           ext2            rw,relatime     0 2  # UUID=44741e0f-924a-4841-80ef-2132bef84182 /dev/sda4               /home           ext4            rw,noatime,discard      0 0   and run sudo mkinitcpio -p linux. It seems to work. I'm able to boot by mounting the partition on the second disk. df shows:  $ df Filesystem      Size  Used Avail Use% Mounted on /dev/sdb3        28G   18G  9.8G  65% /   So, clearly, sdb3 is mounted, not sda3. Here's the problematic step: When I try to format sda3, which is supposedly unused, I get the following:  $ sudo mkfs.ext4 /dev/sda3 [sudo] password for stew:  mke2fs 1.42.11 (09-Jul-2014) /dev/sda3 contains a btrfs file system Proceed anyway? (y,n) y /dev/sda3 is apparently in use by the system; will not make a filesystem here!   sda3 is in use. How and why could it possibly be in use?  As per casey's comment, the output of mount:  mount | grep sd /dev/sdb3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime)   As per Warwick's comment, unmounting:  $ sudo umount /dev/sda3 umount: /dev/sda3: not mounted   Mounting and umounting sda3 elsewhere works successfully, but changes nothing.  Update: More fishy behavior:  $ mount | grep sd /dev/sdb3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime) $ sudo mount /dev/sda3 mnt [sudo] password for stew:  $ mount | grep sd /dev/sda3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime) /dev/sda3 on /home/stew/mnt type btrfs (rw,relatime,ssd,discard,space_cache)   After mounting sda3, sdb3 is no longer mounter. Weird, huh?  As per mikeserv:  $ rmmod btrfs rmmod: ERROR: Module btrfs is in use   This is very much expected, since sdb3 is btrfs and supposed to be mounted to root. From my mkinitcpio.conf file:  MODULES="" HOOKS="base udev autodetect modconf block filesystems keyboard fsck" I am on SharePoint 2013 and do not have access to Designer, as a preface.  I am trying to create a list view that filters items by whether or not they were added in the last hour.  I had done this earlier, only with items that were added in the current week, by creating two columns, 'Week Start' and 'Week End', and filtering by Created falling between those two.  Simple enough.  However, filtering list views does not allow for complex functions, nor does the [Today] function recognize time, causing an issue.  Is there any workaround for this?  Thanks. The mdframed environment fails to break into several pages (slides) when used in a frame environment from the beamer class.  In the other hand, the boitecoloriee environment from the boites package can be broken into several pages.  Here is a document that demonstrates the issue. It should not be compiled directly into pdf because boitecoloriee uses pstricks.  \documentclass{beamer} \usepackage{xcolor,boites,boites_exemples,pstricks} \usepackage{mdframed} \usepackage{lipsum}  \begin{document}  \begin{frame}[allowframebreaks]{Using \texttt{boitecoloriee}}   \begin{boitecoloriee}     \lipsum[1-2]   \end{boitecoloriee} \end{frame}  \begin{frame}[allowframebreaks]{Using \texttt{mdframed}}   \begin{mdframed}     \lipsum[1-2]   \end{mdframed} \end{frame}  \end{document}   Maybe is there a way to fix mdframed to work in slides too. Any clues? Is it safe to put a clothes washer outdoors? What happens if I unsubscribe from Apple Music, then resubscribe at a later date? I want to cancel my apple music subscription for now, but may want to bring it back this summer. Will all the music I added be permanently removed when I unsubscribe, or will re-subscribing retrieve all my previous music? Should I load an entire html page with AJAX? How to prove: if $a,b \in \mathbb N$, then $a^{1/b}$ is an integer or an irrational number? Reference for the subgroup structure of $\rm{PSL}_2(q)$ This material is covered in detail in Dickson's "Linear Groups with an exposition of the Galois Field Theory", chapter XXII and Huppert's "Endliche Gruppen", chapter II, paragraph 8. Since I don't speak german and Dickson's treatment often requires deciphering, I was wondering if there is a "modern" account of this somewhere. Removing non numeric characters from a string What's the difference between  var A = function () {     this.x = function () {         //do something     }; };   and  var A = function () { }; A.prototype.x = function () {     //do something }; Prove universal morphism is unique up to unique isomorphism. How to change Blender's default startup settings? How can I change Blender from the default cube/lamp/camera default setup? Also, is it possible to change other features, such as the default view direction (Top, Side, etc) or the Editor type (3D View, Node Editor, Graph Editor, etc)? On Cesàro convergence: If $ x_n \to x $ then $ z_n = \frac{x_1 + \dots +x_n}{n} \to x $ I have this problem I'm working on. Hints are much appreciated (I don't want complete proof):  In a normed vector space, if $ x_n \longrightarrow x $ then  $ z_n = \frac{x_1 + \dots +x_n}{n} \longrightarrow x $   I've been trying adding and subtracting inside the norm... but I don't seem to get anywhere.  Thanks! Can an observer B move in such a way that his clock will run faster than that of a fixed observer A? My understanding of Special and General Relativity comes from books which attempt to explain them to non-experts in these fields.   Let A and B be observers, which at some time t(0), are together at some location P fixed to the earth's surface. A and B are provided with "clocks", which at time t(0), are identical lumps of the same radioactive element-that has a very long half-life. A and A's "clock" remain fixed to the earth's surface. B and B's "clock" leave A and stay together, but eventually return to A after some interval of time T (as measured by A's "clock"). If, during this time T, B's velocity relative to A is sufficiently close to the velocity of light or B remains close to a sufficiently massive body, it seems that time can "pass more slowly" for B than for A. So that when B rejoins A, B's "clock" will contain more of the radioactive element than A's "clock"   My question is: Are there any scenarios that B together with B"s "clock" can undergo (during the time T) which will cause time to "pass more quickly" for B than for A? So that when B rejoins A, B's "clock" will contain less of the radioactive element than A's "clock". If there are no such scenarios, is there any fact or law in Relativity theory which rules them out? My actual question is to find the number of transversal given a collection of set ...  After a little bit of study it has come down to:  How can we count the number of matchings in a bipartite graph with parts of size $m$ and $n$ such that it covers all $m$ vertices of the first part, $m \le n$?  I already know that there is a way to count the number of perfect matchings in a bipartite graph with $m=n$ using the permanent of its (square) incidence matrix. Which comes first: cat or dog? Which comes first in a sentence?  I know some word pairs such as bacon and eggs, where bacon always comes first. E.g:     Make me bacon and eggs for dinner, honey.   Cats and dogs are the two most common pets I know of. What is the preferred order?   Dogs are superior.     Don't put dogs and cats together, they might fight!  Cats are superior.     Don't put cats and dogs together, they might fight! How do I convert an argument list to a sequence of arguments? Search functionality in lightning:datatable? Is there a way to search across all rows/columns in a lightning:datatable to narrow down the list, just like jQuery DataTables? If so, how do implement that?  Can I somehow do it all on the client-side to make it super fast (some sort of DOM manipulation)  I'm having some issues with the lightning:datatable not updating. I have attached my code below, maybe you can help me spot the issue:  Markup:  &lt;aura:component extends="c:Base" controller="AccountBrowserForm"&gt; &lt;aura:handler name="init" value="{! this }" action="{! c.doInit }"/&gt; &lt;aura:attribute name="selectedAccountId" type="Id" access="public" /&gt; &lt;aura:attribute name="accounts" type="Object"/&gt; &lt;aura:attribute name="mycolumns" type="List"/&gt; &lt;aura:attribute name="sortedBy" type="String" /&gt; &lt;aura:attribute name="sortedDirection" type="Boolean" default="true" /&gt;  &lt;aura:registerEvent name="AccountFilterChange" type="c:AccountFilterChange" /&gt;  &lt;aura:attribute name="backingdata" type="List" /&gt; &lt;aura:attribute name="filter" type="String" /&gt; &lt;lightning:input type="text" onchange="{!c.filter}" value="{!v.filter}" label="Filter" /&gt;  &lt;lightning:datatable aura:id="lightningTable"                      data="{! v.accounts }"                      columns="{! v.mycolumns }"                      keyField="Id"                      onrowaction="{! c.handleRowAction }"                      onsort="{!c.updateColumnSorting}"                      sortedBy="{!v.sortedBy}"                      sortedDirection="{!v.sortedDirection}"                      hideCheckboxColumn="true" /&gt;     Controller:  doInit: function (component, event, helper) {     helper.callServer(component, "c.getAccounts", $A.getCallback(function (response) {         component.set("v.accounts", response);         component.set("v.backingdata", response);         console.log(component.get("v.backingdata") + " /// BACKING DATA INSIDE ")         console.log(component.get("v.accounts") + " // ACCOUTN DATA INSIDE")          component.set('v.mycolumns', [{                 type: "button",                 typeAttributes: {                     label: '',                     iconName: 'utility:add',                     name: 'selectRecord',                     title: 'selectRecord',                     disabled: false,                     value: 'edit',                     variant: {                         fieldName: 'variantValue'                     },                 }             },             {label: 'Name', fieldName: 'Name', type: 'text', sortable: true},             {label: 'Street', fieldName: 'BillingStreet', type: 'text', sortable: true},             {label: 'Postal Code', fieldName: 'BillingPostalCode', type: 'text', sortable: true},             {label: 'City', fieldName: 'BillingCity', type: 'text', sortable: true},             {label: 'Country', fieldName: 'BillingCountry', type: 'text', sortable: true},         ]);          console.log(component.get("v.backingdata") + " *** BACKING DATA OUTSIDE *** ")         console.log(component.get("v.accounts") + " *** ACCOUNT DATA OUTSIDE *** ")     })) },  filter: function (component, event, helper) {     var data = component.get("v.backingdata"),         term = component.get("v.filter"),         results = data,         regex;     try {         regex = new RegExp(term, "i");         // filter checks each row, constructs new array where function returns true         results = data.filter(row =&gt; regex.test(row.name) || regex.test(row.age.toString()));     } catch (e) {         // invalid regex, use full list     }     component.set("v.accounts", results); },   For some reason the filter function is completely unresponsive. Also, does it matter that I'm populating the component with a response from a callback function. @sfdcfox, I noticed in your example that you simple created an array with dummy data. My "myaccounts" attribute is of type object Can the Hubble constant be measured locally?