momentum
rallain | October 9, 2008**Pre reqs:** [Free Body Diagrams](http://scienceblogs.com/dotphysics/2008/09/basics-free-body-diagrams.php), [Force](http://scienceblogs.com/dotphysics/2008/09/basics-what-is-a-force.php)
The time has come to look at things that are NOT in equilibrium. The most basic question to ask yourself is: *"What do forces do to an object"*? Aristotle would say that forces make things move. Constant forces make things move constantly. Actually, Aristotle said there were two types of motion:
Natural motions: These motions don't need anything to happen, they just do. Example: a rock falling. You…
rallain | October 2, 2008I was recently re-watching a MythBusters episode and I found something I had wanted to explore previously (but accidentally deleted the episode). Here is a short clip from the "shooting fish in a barrel" episode:
Did you see what I found interesting? That big barrel of water left the floor from being hit by a bullet.
The question here is: Does a bullet have enough energy to increase the gravitational potential energy of the barrel to that height?
First, let me gather some data. From the episode, the Mythbusters were firing a 9mm pistol round into the barrel. I don't know much about…
rallain | September 13, 2008There is no air resistance in line rider. Sorry to spoil the suspense.
To test for the presence of an air resistance force, a track was created that let the rider fall.
(note the markers on the side. These are used to keep track of how the origin is moving).
Below is the y position of the rider as a function of time:
In this situation, the rider falls about 100 meters. A quadratic line is fit to the data…
esiegel | May 16, 2008This has been all over my inbox since the press release came out yesterday; it's been on slashdot (thanks Brian), it's been at space.com, and there's a mediocre writeup on Universe Today. What's the big news? Black Holes don't destroy information after all!
What is this whole information thing, anyway? Take a look at all the normal stuff in the Universe: photons, protons, neutrons, and electrons, for example. They have lots of different properties each. They move around one another, they get bound and unbound from one another, they exert forces on one another, etc. They're aware of one…
esiegel | May 8, 2008Let's say we're having a nice day here on Earth; the Sun is shining, the clouds are sparse, and everything is just looking like a peach:
And then Lucas goes and tells me,
Oh my God, Ethan! It's Armageddon! An asteroid is coming straight for us! You've got to stop it!
Really? Me? Well, how would I do it? Let's say we've got some reasonably good asteroid tracking going on, and we've got about 2 months before the asteroid is actually going to hit us. We'd like to do something with the situation on the left, to avoid the situation on the right:
Well, what we really have to do is change the…