Saturday, August 13, 2011

True Confessions of a Physics Teacher


I know what you're going to say. It's my job to know these things.

But I will confess, there are so many things to know in physics that it's easy to sort of mmm... pass by topics or ideas that are less intuitive, particularly if they're not that interesting. I've finally come to accept the fact that I haven't grappled with certain standard ideas in physics enough to "own" them in a way that I can explain to students. So this is both a record of my confession and my repentance, meaning I'll list the topics here that have eluded me to some degree and I'll write a bit about them after
I've researched them properly and feel like I own them.

The Hunter and the Monkey Problem
I know... this is classic and I really should already own this, but whatever. Here we go. Here's the gist as put by this website.

When hunting the wiley Stuphedwithstuph Monkey the hunter is always faced with a problem. The Stuphedwithstuph Monkeys have developed a sixth sense that allows them to let go of their branch the instant that a bullet leaves the muzzle of a gun. The age old question among hunters has been "Where should a hunter aim to actually hit the Stuphedwithstuph monkey?
A) Above the monkey.
B) Directly at the monkey.
C) Below the monkey.
The hunters have always believed that they should aim beneath the monkey so that the monkey will drop right into the path of the bullet. Individual hunters all disagree when it comes to how far below the monkey they should aim. Since no one has ever successfully shot a Stuphedwithstuph monkey the question has remained unanswered. Where should you aim?

I feel like that website has done a good job of explaining the correct answer, but here's my shortened version. If you aim at the monkey and there were no gravity you'd hit it, right? If the bullet starts to travel along that line and the monkey lets go at the same instant, both the monkey and the bullet will have deviated from that original line (B in the picture) by the SAME AMOUNT because gravity is working on them equally. Thus, it doesn't matter how far away you are, given enough time and space to fall, the bullet should eventually hit the monkey if you've aimed directly at it originally. At least that's how it works theoretically...

Ok, that took a little time... and in attempting the next topic: diffraction and holography I got bogged down in Instructables and subsequently got inspired to make a ferrofluid. So here are some other topics I hope to research and post about soon:

Diffraction and Holography
Fresnel Lenses
Capacitors in (RL circuitry)
something about standing waves bothers me. Not sure what exactly it is yet.
Virtual Images and the Eye

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