Built on Facts

In daily life, there’s pretty much three kinds of frictional forces that you’re likely to encounter if you classify them by how much they are affected by speed. We’ll not worry about the direction of those forces since for our purposes it’s good enough to say that friction acts in the direction opposite the [...]

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Have you seen The Dark Knight yet? No? What’s wrong with you, go add to its box-office gross now. It deserves it. No, I’m not kidding. Also, stop reading since there’s about to be some minor spoilers.
This post was inspired by my mom, who wants to know how plausible the [...]

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Picture a railroad spike, held vertically as if to be pounded into a railroad tie. Now picture a 14 pound bowling ball poised 35 feet above the spike, and then let drop straight down to hammer the spike down into the ground.
The energy m*g*h works out to about 600 joules, a typical energy for [...]

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I love teaching, but I have to say I am not a fan of teaching the summer session. Everything is way too disorganized. Oh well, at least it’s only for another three weeks or so.
The way undergraduate intro physics is taught is usually in two halves, and right now I’m teaching the second. [...]

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Yesterday I completely forgot to mention the anniversary of the most amazing thing humanity has ever done.  July 20, 1969, Neil Armstrong, Buzz Aldrin, and Michael Collins successfully completed our first steps onto another world.  Though I was born long after their success, I am in absolute awe of them and those who helped make [...]

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See that equation there? It’s the unsung hero of Maxwell’s equations. It says in English, “This is where I would tell you how magnetic fields are generated from magnetic charges, but there aren’t any such thing as magnetic charges.”
In its integral form as above, it’s usually the second of Maxwell’s equations that my [...]

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A few days ago I wrote about how to move in space, you needed to bring along something to push against. Dr. Pion objected. “It’s not what you push against that makes you move, it’s what pushes against you.”, if I can paraphrase.
I thought that was a silly objection. It’s true, but [...]

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A couple days before I started teaching recitation sessions for Physics 208 (the E&M half of calc-based intro physics) this summer, I found out that in fact I was not teaching the second summer session, I’m teaching for the second half of the full summer session. Turns out there is a difference! For [...]

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Note: The comments/permalink issue on this post has been fixed. I have no idea exactly what happened, but it’s not happening anymore which is good enough for me!
I saw Pixar’s Wall-E on opening night. Since even the most mediocre Pixar films are usually among the best in the business, I figured it would be [...]

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A few days ago I wrote a pretty basic post about the trajectories of a football.  Dr. Pion suggested the real physics in football was in the inertia tensor of the ball itself.  True enough.  As such, this post is going to be a little tough in places for people who haven’t seen this kind [...]

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