numerical
rallain | May 12, 2009Maybe you have seen this trick. Basically, you hold by supporting it with two fingers from the bottom. You then move your hand around to keep it balanced while the stick is vertical. It is really not as hard as it looks. Also, there are two things that can make your job easier. Use a longer stick, or add an extra mass at the end of the stick. Here is a video of me demonstrating this. (I forgot, this also an event in the show Unbeatable Banzuke)
Balancing a Stick Demo from Rhett Allain on Vimeo.
So, how does this work? Let me start with a stick that is mostly vertical and supported by…
rallain | February 24, 2009Basically, the title says it all. Here is a short tutorial on projectile motion calculations with a spreadsheet.
Record your screencast online
I left out a lot of details, so maybe these links will help:
Spreadsheet tutorial for numerical calculations (video)
More details on numerical calculations
Projectile motion
rallain | January 29, 2009I really didn't want to post this, but I am going to anyway. I used ScreenToaster.com to make a screen capture movie (with audio) of a tutorial on spreadsheets.
This should accompany my previous post on numerical calculations.
Free online screen recorder
rallain | December 29, 2008In part I of this post, I talked about the basics of projectile motion with no air resistance. Also in that post, I showed that (without air resistance) the angle to throw a ball for maximum range is 45 degrees. When throwing a football, there is some air resistance this means that 45 degree is not necessarily the angle for the greatest range. Well, can't I just do the same thing as before? It turns out that it is a significantly different problem when air resistance is added. Without air resistance, the acceleration was constant. Not so now, my friend.
The problem is that air…
rallain | October 21, 2008[In a previous post, I talked about numerical calculations](http://scienceblogs.com/dotphysics/2008/10/basics-numerical-calculation…). The basic idea is to use the momentum principle and the following "recipe":
Update the position of the particle
Update the momentum of the particle
Update the force on the particle
Looks great, right? Well, it mostly is great. I want to give a couple of pointers about the last step, update the force on the particle. How and when can you do this? Really, in numerical calculations, you will see two types of forces:
Forces that you can calculate: That looks…
rallain | October 16, 2008Maybe you know I like numerical calculations, well I do. I think they are swell. [VPython](http://vpython.org) is my tool of choice. In the post [Basics: Numerical Calculations](http://scienceblogs.com/dotphysics/2008/10/basics-numerical-calculation…) I used vpython and excel to do something simple. I will do that again today (in that this problem could also be solved analytically). However, there is one big difference. This problem has a non-constant forces. Suppose I have a mass that is connected by a spring to a wall. This mass-spring is sitting on a table with no friction.
, [Momentum Principle](http://scienceblogs.com/dotphysics/2008/10/basics-forces-and-the-moment…)
What are "numerical calculations"? Why are they in the "basics"? I will give you really brief answer and then a more detailed answer. Numerical calculations (also called many other things - like computational physics) takes a problem and breaks into a WHOLE bunch of smaller easier problems. This is great for computers ([or a whole bunch of 8th graders](http://scienceblogs.com/dotphysics/2008/09/…
rallain | October 1, 2008I can't remember how I found this, but [Scratch](http://scratch.mit.edu) is a graphical programming language developed at MIT. My kids love this. In order to make sure they don't know more than I do, I created my own scratch program. I am sure someone from the scratch community will attack it for some reason, but I am ok with that.
The program shows a numerical calculation of the motion of a box with a constant force on it. You change the mass and the force. It "sort of" plots the position as a function of time. Don't worry python, I still think you are the best.
Learn more about…
rallain | September 15, 2008I like computers, really I do. Computational physics is a good thing. However, there is a small problem. The problem is that there seems to be a large number of people out there that treat numerical methods and simulations as something different than theoretical calculations. You can tell who these people are because they refer to simulations as "experiments". But what do these simulations really do in science? What is science really all about?
**Science**
To me, science is all about models. Making models, testing models, upgrading models. Models. Some examples are the model of…