center of mass
esiegel | June 22, 2012"Some prophecies are self-fulfilling
But I've had to work for all of mine
Better times will come to me, God willing
Cause I can't leave this world behind" -Josh Ritter
You sure can't leave this world behind. At least, not very easily. The reason for it, of course, is gravity.
Image Credit: Physclips, via the University of New South Wales' School of Physics.
Here on the surface of the Earth, the gravitational potential well is pretty large; large enough that there's no easy way off. Sure, you can pour a huge amount of energy into a rocket to try and overcome this gravitational potential…
rallain | June 21, 2010Of course I am talking about Arnold Schwarzenegger. After looking at how many bullets he carries in Commando, I remembered this scene (also from Commando) (warning: maybe some not great language and some killing. You have been warned)
If you don't want to watch that clip, here is a shot (sorry for the quality).
Clearly Arnold is strong, but there is more than strength involved here. Oh, don't bring your "he did it with wire stuff". I am not buying that. Also, I am talking about THE Arnold - he is real. I am not talking about the character in the movie (not real). Now for some physics…
rallain | June 26, 2009Was the moonwalk fake? No, not the Apollo landings. I am talking about Michael Jackson's moonwalk. You got to admit, he had a big impact on a lot of stuff and this is my way to give him respect - physics.
I am sure you know about the moonwalk. Maybe you can even do the dance move yourself, but how does it work? First, here is a clip of MJ doing his stuff.
As a side note, I can't remember where I saw it but there was a great discussion of the history of the moonwalk. If I recall correctly, some were saying Michael didn't create this move. One thing is for sure, he made it popular. Now…
rallain | February 21, 2009This is one of my favorite demos. Easy to do and doesn't really require any equipment. The basic idea is that you support a meter stick horizontally with two fingers. Slide your fingers in and they will both meet at the center of mass. Here is a video.
Meterstick friction demo from Rhett Allain on Vimeo
So, how does it work? To explain this, you need to understand friction and equilibrium. Well, nobody really understands friction - but anyway..
First, what is equilibrium? Equilibrium means that an object's motion does not change. For this case that means that both it's velocity and it…
rallain | December 1, 2008This is something I have thought about for some time. It is also something I (as a father of 4) have a lot of experience with. The problem is these infant car carriers. In the car they are not a problem. The problem is out of the car. Not sure what I am talking about? Here is a picture:
I don't mean to attack the infant carrier industry. I am sure some people really like these things. For me, there is only two situations that are good for taking the seat out of the car.
In a restaurant. The infant seat works well with those toddler high chairs. Most of the current infant seat…