newton's second law
rallain | January 22, 2010Since my previous post on R2-D2 flying was so popular, I thought I would follow it up. I was going to add these two points in the comments, but a separate post seems to make more sense.
Point 1 - R2 flies at a constant speed
Well, he obviously doesn't always have to fly at a constant speed. However, in the clip I was looking at there are two important things in the analysis. What angle is R2's thrusters at? Is R2 flying at a constant speed? I found a much better quality version of the flying R2 from Billy Brook's site. That helped out a lot. So, on to Tracker Video Analysis (I always…
rallain | January 21, 2010You know I can't help but like Star Wars. Even with the new stuff, I watch it. Recently, I was watching the Clone Wars cartoon and noticed something odd about the way R2-D2 flies. I know what you are saying...."the odd thing is that he flies at all. Why didn't he fly in episodes 4-6?" Who knows. Here is the best image I could get of R2-D2 flying (from wookieepedia).
What is wrong? Well, maybe you can't tell from the image I posted. Here is a diagram of flying R2-D2.
If R2 (I can call him that because we are good friends) was flying like that, why would that be a problem? That would…
rallain | November 4, 2009I already attacked the 2008 Punkin Chunkin Show. So, now I going to give the chunkers some tips. In case you aren't familiar, the Punkin Chunkin contest has teams create devices to launch a pumpkin. They have different categories, but I am going to focus on the air-powered devices. The basic idea is to make an over sized pneumatic potato gun. Here are the things I was inspired to think about.
It seems all the canons were aimed at about the same angle. Did they guess at the angle? Or is this trial and error? What would be the best angle for a pumpkin launch?
Does the optimal angle of…
rallain | October 11, 2009The other myth the MythBusters looked at last week was the phrase "knock your socks off" (along with the dropping and shooting a bullet myth). But before that, let me complain.
Maybe it is just me, but I totally cringe when these guys use the word 'force'. Force probably isn't the best term to use to describe a collision especially when you are talking about one of the objects. "oh, we will just give this object some more force to impact with that other object". Force is not a property of an object, but rather an interaction between two objects. When two things collide, you really need…
rallain | October 6, 2009Many textbooks are pumped up about Newton's 3 laws of motion. For me, not so much. First, (as many other's point out) these are really Newton's ideas about force. Second, the first law is pretty much a special case of the second law. Here are the first two laws (in my words):
Newton's First Law:
The natural state of an object is constant motion.
Yes. I know that is not how it is normally written.
Newton's Second Law:
The rate of change of an object's speed is proportional to the amount of net force on the object and inversely proportional to the mass of the object.
This could also be…
rallain | March 31, 2009What is a fake force? A fake force is one of those forces that introductory texts tell you aren't real - like centrifugal force. They aren't real in the sense that they are due to one of the fundamental interactions. Basically, introductory texts (and even blogs like this one - not a bad summary of real vs. fake forces) attack the centrifugal force. This is because it is so common for students to want to use these faux forces in the wrong way. Better to just not use them at all.
Anyway, there are times when faux forces are awesome. Just to be clear, a faux force is needed to use normal…
rallain | November 19, 2008Rarely am I up late enough to watch the Colbert Report, but by chance I saw it last night. I know Stephen Colbert is a big fan of Dot Physics, and so this is a message to him. Stevie, good job. Here is what he said during his show on the "The Word" segment. Just to give you the context, he was making some point about how if you say anything while talking like a hippie, you make what you said untrue:
Colbert: "Net force of the object equals mass times acceleration, MAN. There. I completely invalidated Newton's second law of motion."
First, the good. He said "net force". How many…