Installing Lubuntu 14.04 on an HP Omnibook 6100
System installation is stalled on Compaq Presario R3000
The Time That 2 Masses Will Collide Due To Newtonian Gravity My friend and I have been wracking our heads with this one for the past 3 hours... We have 2 point masses, $m$ and $M$ in a perfect world separated by radius r.  Starting from rest, they both begin to accelerate towards each other. So we have the gravitational force between them as:  $$F_g ~=~ G\frac{Mm}{r^2}$$  How do we find out at what time they will collide?  What we're having trouble with is this function being a function of $r$, but I have suspected it as actually a function of $t$ due to the units of $G$ being $N(m/kg)^2$.  I've tried taking a number of integrals, which haven't really yielded anything useful.  Any guidance?  No, this is not an actual homework problem, we're just 2 math/physics/computer people who are very bored at work :) How to make \left, \right pairs of delimiter work over multiple lines? I have a very long equation that must be separated into two lines, and it has several pairs of nesting \left \right delimiters. Unfortunately, it seems that they need to be on the same line in order for them to work.  Also I'm using the align environment because I need the aligning functionality. Is there a way to have the size of delimiters automatically adjusted over multiple lines? Was Dumbledore aware that Professor Snape took points from Harry/Gryffindor unfairly? In many situations, we see Professor Snape behave in an unfair manner.   Snape unfairly and arbitrarily takes house points away from Harry/Gryffindors.  Was Dumbledore aware of this and, if so, did he just not care, or did he support this to somehow help Snape's double agent role? Do ground seeds contain oil? StructureMap error when invalid controller I am using Structure map like the MVC storefront by Rob Conery does and I have an AdminController and so to get to it I just type:  website/Admin/action   however if I miss spell the controller name I get the error below:  Exception Details: System.ArgumentNullException: Value cannot be null. Parameter name: key  There error occurs on this line:  Controller controller = ObjectFactory.GetInstance(controllerType) as Controller;   Does anyone have any ideas on how I can handle this error or not allow it to happen at all and maybe just goto a 404 page??  Cheers in advance Unable to check a mdadm RAID1 array, says the file system's read only? I recently migrated a RAID1 from a CentOS 5 system to a CentOS 6 system and ever since when I attempt to perform a check I get the following:  $ echo 'check' &gt; /sys/block/md127/md/sync_action -bash: /sys/block/md127/md/sync_action: Read-only file system   This actually shows up from a CRON too, specifically, /etc/cron.d/raid-check. this is included in the mdadm RPM:  $ rpm -ql mdadm | head -5 /etc/cron.d/raid-check /etc/rc.d/init.d/mdmonitor /etc/sysconfig/raid-check /lib/udev/rules.d/63-md-raid-arrays.rules /lib/udev/rules.d/65-md-incremental.rules   Here I'm running the same command that's used by the CRON:  $ raid-check /usr/sbin/raid-check: line 96: /sys/block/md127/md/sync_action: Read-only file system   This typically runs once a week and sends an email which is what originally alerted me to the issue. But at any rate I'm at a loss why this RAID seems to be unable to be checked.  The RAID seems fine on inspection though.  $ cat /proc/mdstat  Personalities : [raid1]  md127 : active raid1 sda1[0] sdb1[1]       976759936 blocks [2/2] [UU]  unused devices: &lt;none&gt;   I point this out only because while googling I found this thread regarding a bug in mdadm but this was for a older version of mdadm.      Version info  $ lsb_release -d Description:    CentOS release 6.6 (Final)  $ rpm -q mdadm mdadm-3.3-6.el6_6.1.x86_64  $ mdadm --version mdadm - v3.3 - 3rd September 2013 was created on Server Fault, answered on Server Fault, I upvoted some of those answers on Server Fault, and then moved by consensus to Super User.  Now that the question is on Super User, I can upvote the same answers I previously upvoted on Server Fault. How can I make a time delay in Python? Use of capitals and full stops in bullet points Possible Duplicate:          Let's say I have a bullet point list e.g:   Point 1. Point 2.  Point 3.    Notice I have put a capital letter for the starting letter of every bullet point and a full stop at the end. Is this the correct way to do it?  If not, what is the correct way to do it?  Do I put a capital letter and no full stop, or, the other way around, a full stop and no capital letter? Alternatively, do I not put a capital letter or a full stop? Is it only necessary to put a capital letter on the first bullet point and full stop on the last bullet point?  For reference, I'm from the UK so British-English grammar would apply. Prove that $\gcd(a^n - 1, a^m - 1) = a^{\gcd(n, m)} - 1$ What's the easiest way to set up a LAMP stack? I set up a new VPS instance of Ubuntu and am wondering what the easiest way is to get up and running with a basic LAMP stack (i.e. which packages are required, which configuration options need to be tweaked, if any, etc.). "R cannot be resolved to a variable"? Are punches with Gauntlets of Ogre Strength magical, improvised weapon attacks? My Gnoll Paladin just got the Gauntlets of Ogre Strength from Phandelver the other day, and it got me wondering:    Would it be possible/make sense for punches using them to count as an improvised weapon? (Since I'm not punching with empty fists, I'm wearing magical gauntlets) If so, would punches from a person using them count as magical weapon damage? Why doesn't GCC optimize a*a*a*a*a*a to (a*a*a)*(a*a*a)? What makes SHA-256 secure? For example, RSA relies on a mathematically hard problem, factoring, while ECDSA or similar rely on discrete logarithm problem.  What makes SHA-256 and similar hash functions, of the same family, secure against pre-image and collision attacks? What's the math behind it? How to install Telegram Is there a way to avoid "+canned.response" in the email address using Gmail's canned response feature If I set up a filter and send it a canned response, Gmail appends +canned.response to my username in the reply.  For example, given the filter "from:foo@example.com to:me@example.com" set up to send a canned response, when foo@example.com sends me an email the canned response comes from me+canned.response@example.com instead of me@example.com, exposing that I'm using a canned response.  Is there a way to avoid this? I understand that for resistors in series we need to add R for each resistor to get the equivalent resistance, where R is resistance. I also understand the mathematical manipulations that show that for resistors in parallel we need to add the 1/R for each resistor to get the equivalent resistance. However I have a couple of questions that have to do with the physical interpretation of the mathematical manipulations involved.   First, I am trying to understand why in the case of parallel resistors we have to add 1/R's instead of adding R's as in the case of resistors in series i.e. could it be thought that the current in the wire is like a sort of water flow in the pipe that has two horizontal parallel pipes positioned one on top of the other and in between connected by a number of vertical pipes that have a tap each that could be adjusted to represent different resistances. Then at the top of each vertical pipe the water pressure P exists and at the bottom the pressure will be reduced by P*R.   For example, suppose we have three vertical pipes, so then the pressure at the bottom of each (after the tap) is P*R for the total of 3*P*R so why is the equivalent resistance not 3*R*P but 1/R = (1/R1 + 1/R2 + 1/R3) and how can I be able to visualize this relation? Why is there a white space on the left side?  \documentclass{standalone} \usepackage{asymptote} \begin{document} \noindent \begin{asy} size(10cm,10cm); draw((0,0)--(100,100)); draw((0,100)--(100,0)); dot((50,50)); \end{asy} \end{document} Grub not showing on startup for Windows 8.1 Ubuntu 13.10 Dual boot