By second law of motion, acceleration is produced by applied force on a body. Then value of acceleration due to gravity would be different for different bodies on Earth, as the gravity force for them is different?
I'm far from being a physics expert and figured this would be a good place to ask a beginner question that has been confusing me for some time.  According to Galileo, two bodies of different masses, dropped from the same height, will touch the floor at the same time in the absence of air resistance.  BUT Newton's second law states that $a = F/m$, with $a$ the acceleration of a particle, $m$ its mass and $F$ the sum of forces applied to it.  I understand that acceleration represents a variation of velocity and velocity represents a variation of position. I don't comprehend why the mass, which is seemingly affecting the acceleration, does not affect the "time of impact".  Can someone explain this to me? I feel pretty dumb right now :)
Independent Edit/Object mode in splitscreen When I split screen in two and switch Edit/Object mode, they both change. How to change just one? The intention here is:  use one to modelling with numkey view with transparent wireframe and the other to see the progress in perspective, with solid mesh Custom counter steps twice when invoked from caption using caption package Can I get SSD rw performance while keeing data security if I combine SSD & HDD in btrfs RAID1 I have 2 storage devices; classical slow HDD (750GB, /dev/sda) and faster SSD (128GB, /dev/sdb). Currently I have installed Ubuntu &amp; Mint on same btrfs partition on SSD (/dev/sdb5). My btrfs pool consists of /dev/sdb5.  What I want to achieve is data replication on HDD while keeping SSD performance: Something like this:  For read case it would be ideal for procedure to go like this:   read from SSD check checksum if it verifies.. awesome, give me the data if not, fetch data from HDD and perform error correction through duplicate data   I'd manually run (some tool I'm not sure which one... btrfs check --repair perhaps?) every month or so to check HDD checksums and correct them via SSD data against bitrot.  For write case:   write to SSD sync to HDD when write requirements are low, thus not slowing down the system.   Is this possible and how would I do it?  Bottom line is, I like btrfs and would like it to duplicate data across HDD &amp; SSD drive automatically while keeping SSD excellent performance.   Using SSD as write cache is not an option since it's missing data duplication and security. How can I get a list of all packages in a repository section from command line? How can I highlight text before a character with listing? Convergence of $\sqrt{n}x_{n}$ where $x_{n+1} = \sin(x_{n})$ Does $x^{y^z}$ equal $x^{(y^z)}$? If so, why?   Why not simply apply the order of the operation from left to right? Meaning $x^{y^z}$ equals $(x^y)^z$?  I always get confused with this and I don't understand the underlying rule. Any help would be appreciated! Is it always true that $(A_1 \cup A_2) \times (B_1 \cup B_2)=(A_1\times B_1) \cup (A_2 \times B_2)$ Can anyone identify this 90s teen-fantasy series, gems in backbone, big magic, evil king? To hyphenate or not? Style every four posts differently Possible Duplicate:          Is it possible to style every four posts differently? I mean something like this:  &lt;div class="row"&gt; &lt;div&gt;1st post&lt;/div&gt; &lt;div&gt;2nd post&lt;/div&gt; &lt;div&gt;3rd post&lt;/div&gt; &lt;/div&gt; &lt;div class="row&gt; &lt;div&gt;4th post&lt;/div&gt; &lt;/div&gt; ...Repeat   I'm using , so it would be great if I could experiment more with that.. :) I just noticed that the  user edited a ~1 year old  of mine. As you can see, the method call was changed from getSfGuardUser to getGuardUser:    Now I checked the documentation and it seems that the edit is correct.  But how did Community know about that? As far as I know, it is an automated process. Does it have a reference of all possible APIs of languages/frameworks (which seems very unlikely) or is there a routine admins can trigger, for replacing content? Or is it a secret? I would like to use pgfplots to create a figure where I plot curves that have a recursive formula. I tried a very simple case that uses the declare function command to see whether this is possible, and I can't compile (TeX capacity exceeded). Is it even possible to do this?  \documentclass{standalone}  \usepackage{pgfplots}  \begin{document}  \begin{tikzpicture}[   declare function={test(\p)=ifthenelse(\p&gt;1, test(\p-1), 0.5);}, ]     \begin{axis}[]     % use TeX as calculator:     \addplot [mark=none] {x};     \addplot [mark=none] {test(0)};     \end{axis} \end{tikzpicture}  \end{document} Let $A \times \emptyset = \{(x,y)| x\in A, y \in \emptyset \}$. We know there is no element in $\emptyset$. But how does it follow that $A \times \emptyset = \emptyset $? Is it possible to duplicate eyes? This question contains spoilers for anime viewers and early manga viewers.      When Nagato was revived with Edo Tensei, he had Madara's eyes. When Madara was revived, he had his original eyes too (Rinnegan, much like Nagato).   Is this exploitable? Can I repeat this cycle of transplant and revive to duplicate strong eyes? How does that work really? Does the appositive in this sentence need to be set off with commas? On the freelancing website Upwork, there is a US Punctuation and Mechanics test one can take to boost credibility on one's profile for potential clients. These tests are administered by third-party companies that often hire non-native English speakers, so they're known to have some inaccuracies. Unfortunately, because you're allowed to retake the exams after a certain period passes, the correct answers are never revealed. One of the questions on this exam is the following:  Richard’s wife(A) Abigail(B) is an incredibly talented cook(C) and gardener. Comma at (A) Comma at (B) Comma at (C) Comma at (A) and (B) No commas needed  I answered &quot;No commas needed&quot;, but I suspected afterwards that the answer key was looking for the answer choice above it, &quot;Comma at (A) and (B)&quot;. After searching this question online, I found a website with answers for the various questions on the test, and the site claims that &quot;Comma at (A) and (B)&quot; is in fact the correct answer for this particular question. Is the answer key wrong? I feel like there's really no need for any commas, but on the other hand, the appositive Abigail isn't restrictive because it doesn't offer terribly &quot;essential&quot; information, suggesting it could be set off by commas. New to both Ruby and Rails but I'm book educated by now (which apparently means nothing, haha).  I've got two models, Event and User joined through a table EventUser  class User &lt; ActiveRecord::Base   has_many :event_users   has_many :events, :through =&gt; :event_users end  class EventUser &lt; ActiveRecord::Base   belongs_to :event   belongs_to :user    #For clarity's sake, EventUser also has a boolean column "active", among others end  class Event &lt; ActiveRecord::Base   has_many :event_users   has_many :users, :through =&gt; :event_users end   This project is a calendar, in which I have to keep track of people signing up and scratching their name out for a given event. I figure the many to many is a good approach, but I can't do something like this:  u = User.find :first active_events = u.events.find_by_active(true)   Because events don't actually HAVE that extra data, the EventUser model does.  And while I could do:  u = User.find :first active_events = [] u.event_users.find_by_active(true).do |eu|   active_events &lt;&lt; eu.event end   This seems to be contrary to "the rails way".  Can anyone enlighten me, this has been bugging me for a long time tonight (this morning)? How many Shutter Clicks on a New Camera considered normal?    I purchased a quotes new Nikon D750 and checked the shutter count and it has 264 Shutter Clik count on it.    Is that suspect of a returned purchase or used camera? Err http://archive.canonical.com natty InRelease     Err http://security.ubuntu.com oneiric-security InRelease                Err http://extras.ubuntu.com natty InRelease                             Err http://security.ubuntu.com oneiric-security Release.gpg   Temporary failure resolving ‘security.ubuntu.com’ Err http://archive.canonical.com natty Release.gpg   Temporary failure resolving ‘archive.canonical.com’ Err http://extras.ubuntu.com natty Release.gpg   Temporary failure resolving ‘extras.ubuntu.com’ Err http://gb.archive.ubuntu.com oneiric InRelease Err http://gb.archive.ubuntu.com oneiric-updates InRelease Err http://gb.archive.ubuntu.com natty-backports InRelease Err http://gb.archive.ubuntu.com oneiric Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’ Err http://gb.archive.ubuntu.com oneiric-updates Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’ Err http://gb.archive.ubuntu.com natty-backports Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’  Reading package lists... Done W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric/InRelease       W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric-updates/InRelease   W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/natty-backports/InRelease   W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/InRelease   W: Failed to fetch http://archive.canonical.com/ubuntu/dists/natty/InRelease   W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/InRelease   W: Failed to fetch http://archive.canonical.com/ubuntu/dists/natty/Release.gpg  Temporary failure resolving ‘archive.canonical.com’ W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/Release.gpg  Temporary failure resolving ‘security.ubuntu.com’ W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/Release.gpg  Temporary failure resolving ‘extras.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric-updates/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/natty-backports/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Some index files failed to download. They have been ignored, or old ones used instead.   This is what I'm seeing when I try to run sudo apt-get update. I did an update on my instance yesterday and am now experiencing this. Here is what I tried doing:  #!/bin/sh res=`df | awk 'FNR == 2 { print $5 }'` res2=$((res+0))   Here is my error:     -bash: 53%: syntax error: operand expected (error token is "%")   I Googled 'string to int bash' which showed me $((res+0)) but it doesn't work due to the % in the string (53%). How do I convert it in such a way I can do an if statement such as the one below (but that works)?  if [ "$res2" -ge 50 ] then     echo "Your disk &gt;=50% full!" fi