While using the Bernoulli's equation to deduce the upthrust on an aircraft , a statement is always made that     The air particles going above th wing have to cover a greater distance in same time than those going below, so they travel at a higher speed which causes the pressure difference.   But why do they have to cover greater distance? Why do the particles have to meet at the ends of wing again?
I understand that the Bernoulli effect is a flawed explanation for the cause of lift, and does not cause much at all, but how much?   Is there any experimental data on the force caused by the Bernoulli effect? Maybe implicitly through data of the pressure difference between the top and underside of an aeroplane's wings. After that, I assume I could (crudely approximating the pressure to be acting perpendicularly to the flight direction) use $\Delta P A$ to work out the net force on the plane.    Perhaps there is another way to quantitatively analyse the extent to which the Bernoulli effect causes lift.  Edit: see  short cartoon (content similar to Mike Dunlavey's answer).
Two mice heterozygote and black are reproduced. Find the probability of getting the filium dark and heterozygote Map bounded if composition is bounded What is the strict aliasing rule? What is the path of an MTP device in Windows? I am running Windows XP and have a phone mounted through USB by MTP.  In Explorer, its address is:  My Computer\SAMSUNG-SGH-I547\Phone\DCIM   I would like to execute a command line command such as  explorer "My Computer\SAMSUNG-SGH-I547\Phone\DCIM\Camera"   so as to quickly go to the Camera folder. (Right-clicking the device or anything in it does NOT provide a "Create Shortcut" dialog.)  But "My Computer" is not a valid PATH in Windows. Unlike USB flash drives, it seems the phone mounted by MTP does not get a letter drive name.  So, what is the path of an MTP device in Windows?  If the answer is there is no command line path, is there workaround? A cyclic group is a group that is generated by a single element.  That means that there exists an element $g$, say, such that every other element of the group can be written as a power of $g$.  This element $g$ is the generator of the group.  Is that a correct explanation for what a cyclic group and a generator are? How can we find the generator of a cyclic group and how can we say how many generators should there be? I am curious about the proof of these two integrations. It would be great if you could point me in the right direction : $ \int{e^{ax}\cos({bx})dx}= \dfrac{e^{ax}}{a^{2}+b^{2}}[a\cos(bx)+b\sin(bx)] + C $ &amp; $ \int{e^{ax}\sin({bx})dx}= \dfrac{e^{ax}}{a^{2}+b^{2}}[a\sin(bx)-b\cos(bx)] + C $ Why not to extend the set of natural numbers to make it closed under division by zero? We add negative numbers and zero to natural sequence to make it closed under subtraction, the same thing happens with division (rational numbers) and root of -1 (complex numbers).  Why this trick isn't performed with division by zero? Suppose you cut a five year old's hair, save it for 10 years, and then use it for a Polyjuice transformation. What age do you turn into: The toddler or the teenager? How to build a custom kernel? Limit bandwidth used by Windows Update I have a Windows 8 (64-bit, not Pro) machine, and I want to limit the Internet bandwidth available to Windows Update. I read about BITS and GPMC methods, but I don't know how to open the BITS window, and GPMC seems like a Windows Server feature.  How can I control how much bandwidth is available to Windows Update and BITS? SELECT permission on view querying table from another database Find whether the integral converges or diverges. $$\int_{0}^{1}\frac{\log(x)}{1-x^2}dx$$  I simplified it to $$\int_{0}^{1}\frac{\log(x)}{(1-x)(1+x)}dx$$  Here I have $2$ "bad" bounds (both $0$ and $1$).  I think, to prove such integral converges, I should find something that is equivalent to or less than $\log(x)$ so I can exchange them, maybe $\sqrt{x}$, so it may cancel out the fraction, and I can compare it to $$\int_{0}^{1}\frac{dx}{x^p}$$  Also I had an idea to substitute $x$ with $u+1$ so I can use $\log(1+u) \sim  u$ when $u \rightarrow 0$. I'm allowed(not familiar with anything else) to use direct comparision test, limit comparision test, Cauchy test and Abel-Dirichlet's test.   Any hints are much appreciated, I just want to get the big picture.   Thank you. XPath - Get node with no child of specific type How to easily and completely disable/enable WLAN (so it cannot be turned on again while travelling)? Without going into specifics of why I might like to do this, or whether this is a good idea or not, I would like to know how I can disable use of wireless networking on my MacBook Air, either via removal of software or drivers or similar, such that the machine is unable to connect to a WIFI network in any way without I undo those changes.  The intention is for the machine to be unable to communicate wirelessly when out of the house, and for those changes to not be easily reverted until I return (for example requiring some piece of external storage that does not travel with me and which contains copies of whatever I have removed). How can I easily remove and then re-allow WIFI access (without losing my stored profiles/passwords or disturbing anything else)? Is it possible to simply copy a certain app or plugin to an external drive, delete it from my laptop, and later copy it back, again having everything as it was before?  One year later I have been happily using Daniel Lawson's solution below for quite some time now. I have created two applications with automator, one that deletes the .kext, one that restores it from an USB stick. First, copy /System/Library/Extensions/IO80211Family.kext to a USB stick and leave that stick at home. Open Automator, select to create an &quot;Application&quot;, then choose &quot;Utilities&quot; from the &quot;Library&quot;, then &quot;Execute Shell Script&quot;. (I'm translating this from my German menus, so the exact names may differ.) For the &quot;Disconnector&quot; app, enter the following into the text area of the &quot;Execute Shell Script&quot; event: echo YOUR_ADMIN_PASSWORD | sudo -S rm -rf /System/Library/Extensions/IO80211Family.kext  Replace &quot;YOUR_ADMIN_PASSWORD&quot; by your admin password. Then save the app and drag its icon to the Dock. Now, when you are sure you want to be free of all online distractions, click the app icon, and the IO80211Family.kext is gone. Just restart your laptop and you can no longer connect to WLAN:  For the &quot;Reconnector&quot; app, enter the following into the text area in Automator: echo YOUR_ADMIN_PASSWORD | sudo -S cp -r /Volumes/NAME_OF_YOUR_USB_STICK/IO80211Family.kext /System/Library/Extensions/  Replace &quot;YOUR_ADMIN_PASSWORD&quot; by your admin password and &quot;NAME_OF_YOUR_USB_STICK&quot; by the name of your USB stick. Save the app etc. Now when you return home, insert the USB stick that carries the IO80211Family.kext into your laptop, click the Reconnector app icon and then restart your laptop. Now you can connect to WLAN again. Note. There are some security issues invovled when you echo your admin password, because by that it is written to the shell history and can be found there. I don't care, but you might, depending on your circumstances. Can we clarify to the OP that their question is not yet closed and the duplicates are only suggestions? Powering NiChrome wire from battery I'm looking to power nichrome wire from battery. The problem I ran into is that desired length/width of the wire has very small resistance ~ 8 Ohm.  Several kinds of batteries I've tested have internal resistance much higher then that, which leads to wire staying cold and battery getting hot.  Is there any way to increase current drawn from the battery? Some kind of amplifier maybe?  Edit:    1.2V(rechargable) and 1.5V one, while not getting hot itself did not provide enough power to heat the wire. 3V did not provide enough power, even stacking 3 of them in series, only provided about 1V of voltage on the wire, and not enough amperage to heat the wire. 9V battery did provide enough amperage to heat the wire, but at the same time got very hot very quickly itself.   PS. I was wondering if  might work for this purpose? Hardware issue on iMac, flashing question mark I have an iMac 2008/2009 issue and recently the computer would not boot and I would get a flashing question mark. Ran through all the usual steps, try boot in safe mode, flash RAM,  try single user for fdisk, put in OS disk and boot from CD, etc... No dice.   Replaced the hard drive and put the OS disc in the system, press and hold option. (holding C didn't work) I can see the OS disk but when I click on it the system will act like it is going to run and then freeze. The best I got was the OS X disc that changed the screen to dark grey and told be the system had to restart.  Purchased a usb mount for an external hard drive. Was able to mount the old hard drive to a laptop and run disk utility. Everything checked out.  At this point I am pretty sure it isn't the hard drive.   Any other hard ware items this can point too? My iMAC can also "see" the hard drive (and the recovery partition) when connected via the USB and I hold "option" on start up. But it crashes when trying to boot from either.  I am going to take out and re-install the RAM for giggles but I am not sure what else to do.   Ideas are welcome. How can I send mail from an iPhone application I can't seem to find info on installing a Swedish language package on my machine. The language is not listed  and the hits on Google I got led nowhere (or, rather, to the said page).  Where can I ask such a question (within the realm of Stack Exchange)? My dconf/gsettings installation is broken. How can I fix it without Ubuntu reinstall? I run Ubuntu 12.04.1 LTS x64 in VirtualBox. After one very unfortunate misclick (reset saved state instead of load saved state) I got a very annoying problem.  Almost all applications (unity, synaptic, gedit, etc.) print on start:  Using the 'memory' GSettings backend.  Your settings will not be saved or shared with other applications.   And all GUI settings reset after reboot.   Another symptom:  $ GSETTINGS_BACKEND=dconf dconf-editor (dconf-editor:2353): GLib-GIO-WARNING **: Can't find module 'dconf' specified in GSETTINGS_BACKEND GLib-GIO-Message: Using the 'memory' GSettings backend.  Your settings will not be saved or shared with other applications   But /usr/lib/x86_64-linux-gnu/gio/modules/libdconfsettings.so is present.     What I tried (and it didn't help):   sudo apt-get install -f --reinstall  dconf-tools libdconf0 libdconf-dbus-1-0 dconf-service Build dconf-0.5 from sources and make install it Create empty user profile and start programs there   I have to keep current Ubuntu installation so a complete reinstall is not an option for me.   How can I fix it?