It shows..  Required plugin could not be found Video requires to install plugins to play files of the following types: 1 mpeg-4 aac decoder 2 h.264 decoder  It is show in a alert box.  Say answer like download separate and install.
I would like to install the restricted extras package, which I didn't select during the install. How can I do that?        is a meta-package that installs:         Support for MP3 and unencrypted DVD playback   Microsoft TrueType core fonts   Flash plugin   codecs for common audio and video files
Where does the extra kinetic energy come from in a gravitational slingshot? I read in  in this site that the KE a free-falling ball acquires is not originated by the attracting body but that energy was actually stored in the ball when it had been lifted to the height it dropped from.  In this way, it was said, gravity is subject to the conservation of energy principle and cannot change the total energy of an object.  Consider now the maneuver known as a  (also gravity assist) used by space probes such as the . A space probe approaches a planet with velocity $v$, slingshots around, and ends up with velocity $v+2U$, where $U$ is the velocity of the planet.  Consider the energy of the probe. Before, it was $E_i=\frac{1}{2} mv^2$ and after it is $E_f=\frac{1}{2} m(v+2U)^2$. It looks like $E_f$ is much bigger than $E_i$ - but where did the additional energy come from?   Is this not a violation of the conservation of energy principle? How to fix dpkg error [2]? Every time I try to install or remove a package, I get this error. I thought maybe it was the hard disk, but a disk check gave me a clean bill of health. dpkg: unrecoverable fatal error, aborting: reading files list for package 'linux-headers-3.16.0-31': Input/output error E: Sub-process /usr/bin/dpkg returned an error code (2) A package failed to install.  Trying to recover:  I tried the solution of removing the listing for this file from the dpkg status file, but to no avail. I tried purging the package but no use. I'm stuck at this point as nothing I can find on Google helps. Update: This is now what the error says: dpkg: unrecoverable fatal error, aborting: E: Sub-process /usr/bin/dpkg returned an error code (2) A package failed to install.  Trying to recover:  After trying:  Update2: Seems the drive has bad sectors, but the reallocated sector count is 0. The drive is relatively old, however, so I expect some issues. I won't be able to replace it immediately, and until then I would still like to be able to keep the system up to date (especially for security reasons). I noted that there was an issue with coping some md5 checksums related to the package mentioned in the error, but I don't know what to do with those, such as if clearing them would allow dpkg to continue. Windows 7: Disable Lock Workstation After 10 Minutes Using Group Policy On my Windows 7 PC the system becomes locked after 10 minutes of inactivity. Usually I would find this setting next to the screen-saver configuration. The setting is grayed out, however.  I think this is because of corporate group policy. As I am an administrator on this computer I should be able to reconfigure the group policy setting using gpedit.msc.  What is the group policy setting that I need to change to prevent automatic locking of my workstation?  Edit: I don't have configured a screen-saver. I also want to continue to be able to lock the workstation manually. How to mix a jpeg background image with a 3D scene generated using Filmic Blender? I want to compose 3D-model over image, and I use filmic to get more suitable result. But I want the background image to remain in the original colors. So I try to use this setting:    but it haven't setting "look" ("high contrast", "low contrast", ets..) here, so color changes..  How to solve this?  Of course, I can save my render and compose it with jpg-image in different place - no problem here, but my question is about how to make it in place. It will give ability to control colors in filmic color space and see the results immediately.   UPD: image is from image node:    UPD2:     you can't really convert a display referred image to the scene   referred domain; the information has been permanently lost   Ok, but how to make the colors at the output looks close to the original?  UPD3:  This filmic version is from daily build. I am looking for an example of a sequence which shows that, $a_{n+1} - a_n \to 0$ as $n \to \infty$ does not imply that sequence $a_n$ converges. I have a feeling that the sequence should be an oscillatory one but I am unable to think of an example. PHP validation/regex for URL I've been looking for a simple regex for URLs, does anybody have one handy that works well?  I didn't find one with the zend framework validation classes and have seen several implementations. root@SERVER ~$ df Filesystem  512-blocks  Free    %Used   Iused   %Iused  Mounted on /dev/YXCV   655360      365632  45% 6322    13% / /dev/ASDF   3801088     670648  83% 41759   32% /usr /dev/ASR    1048576     500496  53% 5555    9%  /var   How can I pipe the df command's output to only display lines that have more usage than 80%?  e.g.: it would only display:  /dev/ASDF   3801088     670648  83% 41759   32% /usr Java obfuscators I'm looking for a good Java obfuscator.  I've done initial research into the following Java obfuscators: proguard, yguard, retroguard, dasho, allatori, jshrink, smokescreen, jobfuscate, marvin, jbco, jode, javaguard, jarg, joga, cafebabe, donquixote, mwobfu, bbmug, zelix klassmaster, sandmark, jcloak, thicket, blufuscator, and java code protector.  I tried proguard and it has a really nice GUI, seems really stable, and seems to be the most popular, but it seemed to not like some enumeration on a referenced jar file (not within the code I was trying to obfuscate) which was weird.  Yguard seems to require some interaction with ant, which I didn't know too much about.  What is a good java obfuscator?  It doesn't need to be free, it just needs to work well and be easy to use. What is the purpose of the /etc/shadow file in Linux Operating system?  Also, is it same for SUSE clients? There is one shadow cache file is maintained what is purpose of that? I sold an investment in a standard brokerage account at a small loss because I needed the money for a down payment.  I still think it is a good investment, can I buy the same investment in a standard IRA without running into wash sale problems?  I will probably just wait the 30 days any way to avoid any headaches, but I want to know if there is a definitive answer on this.    Being as the cost basis in the traditional IRA doesn't matter, I wouldn't think there would be a problem. Any nice, stable ways to keep a window 'Always on top' on the Mac? I am looking for a stable way to keep any window 'always on top' on OSX.  , an app that does that requires SIMBL/easySIMBL, which it seems is not very stable.  Are there any better solutions? It's actually surprising that there is no native way to implement this. What's the problem with my Young slits experiment? My Young's slits experiment doesn’t work. I mean I tried to see wave effect of light but I didn’t see any thing expect particles! I’ve sent you a pic of my laser and a short video of the experiment. Is there any problem you think? I know that this machine does not work, via thermodynamics. I am asking for an analysis in terms of mechanics and magnetism.  Anyway, so here is the machine:   (source: )    The magnet (the red ball) pull the ball up the ramp, and then it drops the ball through the hole, which then rolls down, and go ups the ramp again. Thermodynamics shows that this can not work.  From a mechanics and magnetism perspective, what happens when you do this, and why can't it happen?  I have a source saying that it would work if it were frictionless and we didn't try to extract energy from it (), so in a certain sense, it is very close to possible (they didn't provide a full analysis though.)  Another Image: Information about (simple) mask wearing (concerning covid19) is a complete mystery to me. On several official places it is not recommended for a person without symptoms to wear a mask. For example:    (time 0:20)  or here:    However no explanation is given - which makes me wonder (and even angry). I think everybody should wear a mask because:   Many persons feel ashamed wearing it, even those with symptoms. If everybody wears it, they do not feel ashamed and wear it. As far as I know, one is (wrt covid19) contagious before developing symptoms. So if everybody wears the mask also these people do.   The two above points act as a collective protection.   Simple mask certainly will lower "getting / spreading illness" probability. Of course the "holes" (in a simple mask) are too big to prevent completely virus to enter (or get out when coughing), but it lowers probability! Even if it lowers the transmission probability by e.g. 5%, it might be a lot. As a hypothetical example: it might reduce R0 from 1.02 to 0.97 and so stop the virus spread so fast.   The videos are full of self-contradiction. In the same video    time 0:50 the lady says I should wear a mask if I am in contact with an infected person... why if it is inefficient?  Question: What are reasons for not recommending wearing a mask? a cold vs flu / the flu Have you got a cold? Have you got flu? Have you got the flu?  Why can't we say a flu or the cold in the previous examples? Adding objects algorithm in Objective-C How to parse data in JSON format? Metric is continuous function Let $X$ be a metric space , $d$ is the metric , show that $d$ is a continuous function from $X\times X$ to $R$.  I think the definition is all we need , but I just don't know where to start , can anyone help me. Can "Mr", "Mrs", etc. be used with a first name? Chinese Passport Holder Transit in South Korea A Chinese passport holder with a US visa has a flight scheduled from Beijing to Los Angeles in mid-November.  This person wants to go to South Korea for a 3 day conference; the conference is one week prior to the PEK-LAX flight.  If this person buys a round-trip ticket from China to Korea, will the transit visa be sufficient? Or will they need a regular visa?    Extra info:  What if the original ticket were modified to make it ICN-PEK-LAX?  . It says "Holding a confirmed onward flight ticket for departure within 30 days." Would a return ticket to China than a flight to LAX a week later be sufficiently "onward"?