So simple:  Will this sail-based moving system work? Why?
How it this possible? Even if the gif is fake, the Mythbusters did it and with a large sail it really moves forward. What is the explanation?
A geometry question: Let $ABCD$ be a convex quadrilateral. Prove that AD is parallel to BC. Let $ABCD$ be a convex quadrilateral such that the length of the segment connecting midpoints of the two opposite sides $AB$ and $CD$ equals $\frac{AD+BC}{2}$ . Prove that AD is parallel to BC. I assume that AD is not parallel to BC but I can't find any contradiction. What's the difference between "uname -r" and "uname -v"? Where were the Avengers during Iron Man 3? The product of $n$ consecutive integers is divisible by $n$ factorial How can we prove that the product of $n$ consecutive integers is divisible by $n$ factorial?     Note: In this  and the comments here the OP has clarified that he seeks a proof that "does not use the properties of binomial coefficients". Please post answers in said newer thread so that this incorrectly-posed question may be closed as a duplicate. Installing an HP Laserjet 1000 I've already installed hplip, it printed a test page, but it won't print from any program. It shows the printer in the list of printers, and it's checked as the default printer. I've restarted a couple times.   When I plugged the USB cable for the printer into the computer after installing hplip, it said printer detected. Then after a couple seconds it said the printer was ready for use.   When I send something to the printer, a pop-up shows that a document was sent to the printer - but there's a triangle with an exclamation point in it next to the message. A few seconds another pop-up indicates that the printer has completed printing the job but it didn't print anything. Would you please tell me which of the following terms is correct? If both are correct, are they equal?     I have no [...] I don't have any [...] I have a large hole in a mesh that I'm trying to fill:    I've been trying an approach like this:    I'm finding it quite tough, since the number of vertices around the perimeter of the hole don't match a grid.  Is there a better approach to filling a hole like this? What do the symbols on the main menu mean? If you swipe all the way to the left on the menu and then some, this sequence of symbols appears. (Do not pay any mind to the white circles: it's where I was holding my finger. The space between the first few and the last three symbols is also not present in game.)    What gives? How to set date format when manually inserting date on excel, without changing regional settings? As expected, Nvidia drivers have reduced my customizations. I can't login to Unity 3D session. I can't find any content to help me to uninstall the driver and I don't know what to do as I have never uninstalled them before. A gerund or use a regular noun? Which of these is correct or more natural?        One of my greatest strengths is critically analyzing.      One of my greatest strengths is critical analyzing.     One of my greatest strengths is critical analysis. The Monty Hall problem Probably a basic issue, but still something that irks me and I can't find an answer online. I want to change the default folder for saving new shapes/processing outputs from &quot;last used folder&quot; to &quot;project folder&quot; or &quot;something in relation to project folder&quot; - is this possible? If so, how can I achieve this? Use of # a.k.a. read-macro How do I become a Werewolf? I've heard that one of (maybe the only?) secret races in this game is a werewolf.  How do I become a werewolf?  And by extension, how do I cure lycanthropy, that is, if there even is a cure? $\mathbb{F}_p[X]/(X^2+X+1)$ is a field iff $p \equiv 2 \bmod 3$ No room for a new \dimen I have this error message:  ! No room for a new \dimen . \ch@ck ...\else \errmessage {No room for a new #3}                                                 \fi   which I can not find a cure for. Definition of textbook RSA In Windows there’re perhaps only a couple of important folders (by important I mean important in my logical picture of the Windows file system) in the installation drive (in my case C:\). Namely Program Files and Windows. I simply stay away from Windows folder and the “add remove program files” is good enough to handle the program files folder of Windows. Of course there’s a folder named Users where the users (who are not admins) can access only their folders.  Thus there’s a clear picture at some level in my mind of the Windows file system. In Ubuntu, when I reach the location /, there’s a huge list of folders, most of which I have no clue as to what they contain. The /bin folder seems to be the equivalent of the Windows folder in windows. The /usr folder seems like it’s the equivalent of the Users folder in Windows. But even the /home folder looks like it can fit the bill.  Please understand that I do understand, that Ubuntu (Linux) has a different character than that of Windows, i.e., there need not be exact equivalent of Windows functions, in Ubuntu. All I am looking for is a bit more clearer picture of the Ubuntu file system.   This question is a part of a bigger question which I am splitting up to make it more answerable. The original question can be found here: "As part of" versus "as a part of"