I am thoroughly confused as to how exactly radial, tangential, and linear accelerations of points on a rotating wheel relate to each other. Every time I think I know what they mean individually, I find a source that tells me that no, that is wrong. I was actually writing down in this post what I think is correct, only to realize that I was writing the same thing for two obviously different concepts.  First, is radial acceleration the same as centripetal and tangential the same as linear?  Second, how do these different accelerations relate to each other on a spinning disk? I was reading through my textbook, and I think I understand angular velocity perfectly in this context. However, I do not understand, for example:     If a disk rotates at a constant angular velocity, why does a point on the rim have radial but not tangential acceleration? Mathematically, this makes sense (since $a=r\alpha$, so if $\alpha=0$, then so must $a$), but not conceptually. Does it have radial/centripetal acceleration simply because it is still exhibiting circular motion? Would the linear acceleration change––is there any linear acceleration?   Basically, I do not really understand how radial, tangential, and linear accelerations relate to each other? I have just a big salad of greek letters in my head.
To my knowledge there are three types of acceleration when a body (e.g. a rod) is moving in a circle about an axis. These are:   Angular acceleration : this is the rate of change of angular velocity. Tangential acceleration : this is the linear acceleration of the system in a tangential direction to the circle and equals the radius times the angular acceleration. Radial/centripetal acceleration : this is the linear acceleration of the system that is directed inwards towards the center of the circle.   I also think there are two types of velocity:   Linear velocity: this is its velocity in the tangential direction and is constantly changing Angular velocity or angular frequency: this is the rate of change of angle.   Is the above correct? And have I missed anything?
I read about the new fancy progress bar which was added to apt 1.0 in  and how to enable it . However on running sudo apt-get update, I did not see the fancy progress bars. On reading the second link again, the solution explicitly requires you to use sudo apt update.  Hence my question is the difference between apt and apt-get. I thought they were one and the same. Randomly selecting elements without repetition Radius of convergence of $\sum_{n=0}^\infty n!x^{n^2}$ The question is to calculate the radius of convergence of $\sum\limits_{n=0}^\infty n!x^{n^2}$.  I dont know how to calculate R.O.C for such type of questions involving $n^2$ as power of x. How do we do this? Any help appreciated. Difference between "I have got" and "I have gotten" Age of universe? Well relativity teaches us that time interval between two events is a frame dependent quantity, then how can we say that our universe is 13.8 billion years old? Should it not depend on who is asking this question? Parsing JSON from URL Edit:  Of course my real code doesn't look exactly like this. I tried to write semi-pseudo code to make it more clear of whay I wanted to do.  Looks like it just messed things up instead.  So, what I actually would like to do is this:  Method&lt;Interface1&gt;(); Method&lt;Interface2&gt;(); Method&lt;Interface3&gt;(); ...   Well ... I thought that maybe I could turn it into a loop using reflection. So the question is: How how do I do it. I have very shallow knowledge of reflection. So code examples would be great.  The scenario looks like this:  public void Method&lt;T&gt;() where T : class {} public void AnotherMethod() {     Assembly assembly = Assembly.GetExecutingAssembly();      var interfaces = from i in assembly.GetTypes()     where i.Namespace == "MyNamespace.Interface" // only interfaces stored here     select i;      foreach(var i in interfaces)     {         Method&lt;i&gt;(); // Get compile error here!     }       Original post:  Hi!  I'm trying to loop through all interfaces in a namespace and send them as arguments to a generic method like this:  public void Method&lt;T&gt;() where T : class {} public void AnotherMethod() {     Assembly assembly = Assembly.GetExecutingAssembly();      var interfaces = from i in assembly.GetTypes()     where i.Namespace == "MyNamespace.Interface" // only interfaces stored here     select i;      foreach(var interface in interfaces)     {         Method&lt;interface&gt;(); // Get compile error here!     } }   The error I get is "Type name expected, but local variable name found". If I try  ...     foreach(var interface in interfaces)     {         Method&lt;interface.MakeGenericType()&gt;(); // Still get compile error here!     } }   I get "Cannot apply operator '&lt;' to operands of type 'method group' and 'System.Type'" Any idea on how to get around this problem? Unable to change privacy settings upon install of Ubuntu 18.04 LTS Are numbers in which all substrings are primes finite regardless of base? I am trying to evaluate the following:  $\displaystyle \int_{0}^{\infty} \frac{1}{1+x^a}dx$, where $a&gt;1$ and $a \in \mathbb{R}$  Any help will be much appreciated. What's the regular expression that matches a square bracket? I tried the Chrome development version for a few days, didn't like it because my tabs became broken and wouldn't load properly. I changed back to the live version, but I forgot to uninstall the development version, which gave me 2 chrome icons on my task bar, but they would both load a broken version of Chrome. I then uninstalled Chrome through the control panel and reinstalled the live version, but I now have one of those broken links on my task bar (a blank page with a folded corner) that points to a version of Chrome that's no longer there. Is there a way to remove this icon? How can I make a copy of a material? How to connect to my web server? Could humans choose to establish fibre digesting colonies in our guts? Invalid signature for Kali Linux repositories : "The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository" Given a command that changes its behaviour when its output is going to a terminal (e.g. produce coloured output), how can that output be redirected in a pipeline while preserving the changed behaviour?  There must be a utility for that, which I am not aware of.  Some commands, like grep --color=always, have option flags to force the behaviour, but the question is how to work around programs that rely solely on testing their output file descriptor.  If it matters, my shell is bash on Linux. How to use Stokes theorem in the presence of holes? Find the value of $\int_{-\infty}^{\infty} \frac{e^{-x^2}}{1+x^2} dx$ . Find the value of $\int_{-\infty}^{\infty} \frac{e^{-x^2}}{1+x^2} dx$     My attempt  First, I know the existence of this integral since $$ \mid \int_{-a}^{a} \frac{e^{-x^2}}{1+x^2} dx \mid \;\; \leq\;\;  \mid \int_{-a}^{a} \frac{1}{1+x^2} dx \mid$$  Next, let $R &gt;0 $ be an arbitrary and $\gamma_1(t) = -R(1-t) + Rt , \;\; 0 \leq t \leq1$ and $\gamma_2(t)= Re^{i\pi (t-1)}, \;\; 1 \leq t \leq 2 $.  So, take $f(z) = \frac{e^{-z^2}}{1+z^2}$.   I tried to find the value or upper bound of norm of $$\int_{\gamma_2} \frac{e^{-z^2}}{1+z^2} dz$$.  However, $$ \lvert\int_{\gamma_2} \frac{e^{-z^2}}{1+z^2} dz\rvert \leq  \frac{\text{max}\lvert e^{-z^2}\rvert}{R^2-1}\pi R = \frac{e^{R^2}}{R^2-1}\pi R $$ So, I can't proceed this.  May I ask you how to solve this? An equivalence relation is defined by three properties: reflexivity, symmetry and transitivity.  Doesn't symmetry and transitivity implies reflexivity? Consider the following argument.  For any $a$ and $b$, $a R b$ implies $b R a$ by symmetry. Using transitivity, we have $a R a$.  Source: Exercise 8.46, P195 of Mathematical Proofs, 2nd (not 3rd) ed. by Chartrand et al