In a given reference frame where object 1 (with known mass and velocity) collides elastically with object 2 (with known mass and velocity), can we identify which object loses kinetic energy? Is it always the more massive one? The faster one?
It has come to the point in my computing program now where I have 5 swinging pendulums that are all modified at once by slider values. These values are drawn onto the from and passed through the class pendulum. To change the values the update button is run, and their is a default option to use a setup that works. The values are also shown on screen through some simple labels. The zero button sets all values (except length) to zero.  The values for each pendulum drawn is:   String length angle Acceleration (angular) Angluar velocity Damping or friction Gravity   My calcuations for these values: (Bob = the weight at the end of the string, and there are X and Y Co-ordiantes for it.  bobX = originX + (Math.Sin(angle) * length);         bobY = originY +(Math.Cos(angle) * length);   Caclulate Acceleration:  Angular Acceleration = (-1 * gravity / length) * Math.Sin(angle);    Increment Velocity:          Angular Velocity += Angluar Acceleration;   Increment Angle          angle += AngularVelocity;   Friction action, pendulum eventually 0's          AngularVelocity*= damping;   Now my next task is to make the pendulums collide "realistically" and recreate a newtons cradle type effect. I've looked into elastic collision solutions on particle e.g. here is an excellent example:    I've also looked at the raw physics behind it  but my brain couldn't get to grips with the raw physics side of things.  So I'm wondering if anybody could help me figuring out the theory for the collisions.  My current idea is when the co-ordinates meet the velocity will simply change polarity e.g. +10 to -10 in the opposing pendulum. Am I correct here?  If you are into code I've posted the code on stack overflow
Why is fundamental group insufficient to classify manifolds? I have heard that some issues in group theory prevent classifying all manifolds upto homotopy using the fundamental group invariant. Does anyone know what are those issues?  Thanks, K. I've recently run into many questions where to author asks several related questions in one post, many of them asked before.   I'm wondering what out policy is on such questions:   Should I vote-close them as being not constructive? Should I vote-close them as duplicates? Should I leave them be? Or even suggest an answer?    - Each of the questions: Waiting for an AJAX request with selenium, and headless browsing in selenium have been asked here before, but he asked both in one.  I've done my best to search for similar questions here in meta but I was unable to find any, reading appreciated. I want to draw a table and i used the following code  \begin{table}[htbp]  \centering \caption{Ship simulator required inputs} \begin{tabular}{|c|c|} \hline L_{PP},  L_{WL}, L_{OS}, B, T, T_{a}, T_{f}, C_{B}, D_{P}, `\\` Bulbous bow, Number of bosses, brackets, thrusters. &amp; ship particulars `\\` \hline Required speed or propeller rpm, ship course angle &amp; Mission data \\ \hline BN, weather angle, water temperature &amp; Environment \\  \hline \end{tabular}% \label{inputs}% \end{table}%`   the result of this is as shown in figure    How can i complete the right border of the table ??? I used \\ to break the line of first row How do you do load testing and capacity planning for databases? This is a  about capacity planning for databases. Related:      I'm looking to create a canonical question of tools and methods of capacity planning for databases. This is intended to be a canonical question. Obviously, the general workflow is:  Put your scenario in place Add monitoring Add traffic Evaluate results Remediate based on results Rinse, repeat until reasonably happy  Please feel free to describe different tools and techniques for different web-servers, frameworks, etc., as well as best-practices. The ring $\Bbb Z\left [\frac{-1+\sqrt{-19}}{2}\right ]$ is not a Euclidean domain Let $\alpha = \frac{1+\sqrt{-19}}{2}$. Let $A = \mathbb Z[\alpha]$. Let's assume that we know that its invertibles are $\{1,-1\}$. During an exercise we proved that:     Lemma: If $(D,g)$ is a Euclidean domain such that its invertibles are $\{1,-1\}$, and $x$ is an element of minimal degree among the elements that are not invertible, then $D/(x)$ is isomorphic to $\mathbb Z/2\mathbb Z$ or $\mathbb Z/3\mathbb Z$.   Now the exercise asks:     Prove that $A$ is not a Euclidean Domain.   Everything hints to an argument by contradiction: let $(A, d)$ be a ED and $x$ an element of minimal degree among the non invertibles we'd like to show that $A/(x)$ is not isomorphic to $\mathbb Z/2\mathbb Z$ or $\mathbb Z/3\mathbb Z$.  How do we do that? My problem is that, since I don't know what this degree function looks like, I don't know how to choose this $x$!  I know that the elements of $A/(x)$ are of the form $a+(x)$, with $a$ of degree less than $x$ or zero. By minimality of $x$ this means that $a\in \{0, 1, -1\}$. Now I'm lost: how do we derive a contradiction from this? Remotely changing hard drive boot order, windows 7 I have one workstation chassis with two hard drives.  Depending on which one I boot from, I get one of two different operating systems: both are windows 7, but they have different static IPs, serve totally different purposes, etc.    The workstation has a modern asus motherboard, core i7 intel CPU, 32 GB ram.   Is there a way to remotely change which hard drive is booted from on a reboot?  Both systems have remote users, and i'd like a solution that is more elegant than being physically present and selecting boot order manually. I'm wondering how it is correct to structure sentence and what punctuation should be used. In particular, is the next sentence correct:     I was wondering if there's any progress on the issue.    Or should I put a question mark in the end of it. Also, can it be restructured to:     I was wondering: is there any progress on the issue? I have this rule in my iptables:  iptables -A INPUT -s 192.168.11.0/24 -j LOG   My question is:  Where is the iptables log file, and how can I change that? I am an Indian citizen. I am flying from Toronto to New Delhi. I have two transits: one at Lisbon airport and the second one at Madrid airport.  While the Consulate of Portugal has assured me that I do not need an airport transit visa during my 2 hours stay in Lisbon airport, I did not get a definitive answer from the consulate of Spain in Toronto.   At Madrid airport, I need to make a transfer from Terminal 2 to Terminal 1.   Does anyone here know whether I need to pass through immigration while making this transition in Madrid and if so, do I need a Schengen visa for that? In many languages, including English, the most important verbs are irregular. Examples include:   to be  to do  to get  to go  to have  to make   The same applies (roughly) to many other languages I know about (Dutch, German, French, Spanish, Swedish) and presumably to many other languages too.  Is there any reason why these everyday verbs tend to be irregular? How does item level and rarity affect the possible attributes? Shape of the universe? What is the exact shape of the universe? I know of the balloon analogy, and the bread with raisins in it. These clarify some points, like how the universe can have no centre, and how it can expand equally everywhere in all directions. But they also raise some questions, like if you are on the surface of a balloon and travel in 1 direction, you will eventually return to your starting point, is it possible our universe have this feature?  If it has, or had, would this be a symmetry of sorts ($\psi(x)=\psi(x+R)$), and as such have a conserved quantity associated with it (by Noether)? Assuming "small curled up dimensions" wouldn't these dimensions have this type of symmetry, what are the associated conserved quantities? Is it known exactly what the geometrical shape of the universe is? (on a large scale) (I am not talking about only the observable universe). How does one define the "size" of a dimension, is this scale only applicable to curled up ones? Is it possible to describe to a layman the shape of the universe without resorting to inept analogies? Should I include a link to my Stack Overflow profile on my résumé? I'm trying to write a script which creates a Nurbs path curve, bevels it, and then stores the location of each vertex/point in that curve. I've been writing it based on the code displayed in the info panel, but it doesn't show what the vertices are supposed to be called - so I can't refer to them in the script.  Update: After following Ratt's links, I modified  for Nurbs Path and am now stuck again, though it's still progress. Below is one version I tried out, but the error message says that Curve has no attribute path_points. Of course it doesn't, because I made that up because I don't know what the Nurbs Path equivalent for bezier_points is.  import bpy import random  def pathPointLoc(cu, typ, points):      for (n) in enumerate(points):         nurb = cu.path_points[n]         print(nurb.location)      return  cu = bpy.data.curves.new("MyCurve", "CURVE") ob = bpy.data.objects.new("MyCurveObject", cu) scn = bpy.context.scene scn.objects.link(ob) scn.objects.active = ob  cu.bevel_object = bpy.data.objects["BezierCircle"] cu.taper_object = bpy.data.objects["BezierCircle"]  pathPointLoc(cu, "NURBS", [(0,0,0,1), (0,0,1,random.randint(1,4)), (0,1,1,1), (1,4,1,1)] ) Is there a program to mount all of my drives automatically? block certain dangerous commands? In my  High school there are few computer having Ubuntu 14.04 installed and many students know the Root  password, how  can I block/disable  certain dangerous  commands like :- rm -rf / rm -rf * :(){:|:&amp;};: to avoid Data loss ? Gauss circle problem : a simple asymptotic estimation. Should seemingly arbitrary things like "play piano for Church" or "intramural badminton" go on M.S. or PhD applications in sciences/engineering? And if they should, I assume that these things should go on a resume under something like "Activities and Community Service". I mean I consider being able to sight read music to play at my Church as a significant feat (how many people can do that?) and might sway one person on an admissions committee if he or she enjoys music and understands how hard one must have worked to accomplish this.   Badminton?.... perhaps not so much Which parts are from Eminems real life? In "" we saw how Bunny Rabbit got into the rapping gang and won the heart of millions of rap lovers. Now in Eminem's original life too similar thing happened. We know how Dr. Dre helped him getting into an industry which is dominated by mainly black people in USA. In fact,  called the film semi-autobiographical. So I want to know which parts are direct picturisations of his real life? I continue to find it amazing that something as “bulky” and macroscopic as a static magnetic or electric field is actually a manifestation of virtual photons.  So putting on your QFT spectacles, look closely at the space near the pole of a powerful magnet – virtual photons! Now look between the plates of a charged capacitor – virtual photons again!   But if it’s all virtual photons, how do we get the difference between a magnetic and electric field?  [This question needs the tag "magnetostatics" as well].