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Archive for November, 2007

Ahh…this will be a pretty random and incoherent post.  All of that turkey in my system is making me sleeepy. : ]

So during the Black Friday rush, my dad got me a Jabra Bluetooth Headset.  After playing around with it, I started wondering about how this wireless connection is formed in the first place, allowing me to “control” my cell phone/computer/etc. from a distance.  It turns out that data is transmitted via low-power radio waves at a frequency of 2.45 gigahertz. Bluetooth devices send out pretty weak signals of only 1 milliwatt, avoiding interference with other systems like your TV or telephone (we wouldn’t want that happening!)  The low power also explains why the operating range is only up to 33 feet.

I Have a Blue Tooth From Eating Mint Chocolate! xD

Another item of interest to me was how a single Bluetooth headset could connect to several devices at once and still function normally.  One might expect all of those emitted waves in that little bubble with a 33 ft radius to interfere with each other.  However, Blue uses a spread-spectrum frequency hopping technique to minimize such a possibility.  Basically, the device “hops” between 79 randomly selected frequencies in a certain range 1,600 times a second!!  So it is very very unlikely for two devices to have the same frequency at the same time, preventing creation of a new wave pattern from two or more waves.

Hope everyone had a nice Thanksgiving!!  If you have some spare time, why not start getting into the holiday spirit and spice up those carols with a bit of physics knowledge? 😀

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In learning about Fluid Mechanics, I couldn’t help but recall an interesting episode over the summer involving a water bottle.  My family and I were at the Water Park and my brother, for reasons unknown, decided to poke a hole in the side of his plastic water bottle.  Perhaps a physics deity coerced him into doing it. 

water-bottle.jpg

If that weren’t foolish enough, he also decided to lose the cap meaning that he had to start drinking, quickly!  Which he decided to do the slow way, though the teensy little hole.  Assuming that the velocity of the slowly sinking level of water was 0 m/s and with measurements of the distance from the surface of the water to the ground and from the punctured hole to the ground, it’s possible to calculate the velocity of the spouting water with Bernoulli’s equation.  The pressure would be equal to atmospheric pressure at a value of 101.3e5 Pa.

P1 + ½ ρv12 + ρgh1 = P2 + ½ ρv22 + ρgh2

I imagine that it would take an extremely long time to finish a bottle of water this way.  Very painful for the neck too.  And not very efficient if you were dying of thirst.

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Moon Orbits

After an exhausting day of debating (in which evidence books and papers serve other purposes besides demonstrating gravitational potential energy ^ ^), I was much too tired to do almost anything.  Going walking in Waikiki and looking at the moon not included of course. 

There was a tiny sliver of a moon visible, currently in a waxing phase.  That got me thinking about orbits.  If it were a circular orbit, we could use the radius (distance from the center of Earth to the center of the moon) and mass of the Earth to figure out the amount of time it takes for the moon to complete one orbit and its velocity.  If it were an elliptical orbit, we’d first have to calculate the semi-major axis.

At a younger age, it always seemed so magical when the moon seemed to follow you.  Now we know that because the moon is not traveling at a great enough velocity to escape the gravitational attraction of Earth, it stays in orbit. : )

moon.jpg

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So after nearly five hours stuck in a classroom taking the SAT, I promptly went home and slept for another five hours…I stick to my claim that standardized testing is a soporific drug.  (But at least I’ll never have to take it again!)

And since an analog clock is an impeccable example of uniform circular motion, it’s possible to calculate many, many things. : )

For one, the angular displacement for any hand of the clock over this 10-hour block of time would be 20π rad.  As for angular velocities, the measures would be -π/30 rad/s for the second hand, -π/1800 rad/s for the minute hand,           and -π/21600 rad/s for the hour hand.

Clocky!

And then at night, it started raining and thundering. ^ ^  Most beautiful thing ever.  Lightning occurs as a result of the electrical current flowing between the Earth and storm clouds (in which electrostatic charge has been building up).  That’s really all I know right now.  But…after learning more about electromagnetism, I shall expand on this. : )

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