Blog 11: "MagSafe," or US Patent No. 7311526

Prior to the January 10, 2006 introduction of the MagSafe connector by Apple, Inc., laptop users worldwide were faced with the potential horror of this:

This gory carnage brought to you by http://en.wikipedia.org/wiki/MagSafe

A terrible disaster awaited every avid Macbook user: if the power connector was pulled out at any disagreeable angle, the entire male-female connection would be ruined. And God help you if you happened to trip on that forsaken wire.

The MagSafe revolutionized laptop recharger connection port safety with the brilliant innovation of a magnetic connection between port and connector. But how would such an invention work? 

Before I answer the question, a few action shots.

Always practice safe charging.

A fool's postulation would insinuate that the connector is charged with a 'north' magnetic charge - and the port 'south,' or vice versa - thus creating a magnetic attraction between the two. This could not possibly be true, for a magnetic monopole is a hypothetical creation still ten million years away from the MagSafe's construction.

Therefore, the only plausible construction of the MagSafe would be for either the port or the connector to be magnetically charged, and the other made of an uncharged yet ferromagnetic material. And by 'ferromagnetic material,' I mean a material that contains atoms with elections that have unpaired spins that create domains that align when in the presence of a stronger magnet. 

But which one is the magnet, and which is merely the ferromagnetic material? Well...

A few paper clips enhance my understanding.

This makes sense, because if the connector was a magnet, it could pick up many bits of ferromagnetic material and create the potential for a short circuit. But short circuits are from another chapter.

Blog 10: Light Bulbs, Inc.

Light bulbs are not very interesting. In fact, they can be downright annoying to replace, especially if they're in hard-to-reach areas. So how could they possibly be interesting?


We've all seen the curly CFLs, the rod-like fluorescents, and the futuristic LEDs. But the most basic of all is the incandescent. And those are the most boring of all.


Not exactly. I found two different makes of incandescents, the typical lamp bulb, and a flood-light. It was an odd experience to hold these fragile things that have hung overhead and out of reach.

Light of my life.

Big boy.

Besides the obvious size and structural differences - the flood-light is top-heavy and its sides are heavily frosted to 'focus' light outward - something completely unrelated to physical form makes the flood-light brighter: wattage. 


Okay, the flood-light is 65 W while the lamp bulb is 52W. But what does that even mean?


Well, as with everything, the inside is what matters most. Within both bulbs are filaments of tungsten. However, the flood-light's filament is thicker than that of the lamp bulb. A thicker filament provides more room for electrons to move through it, and thus enables more current to flow through the wire with a given voltage difference. More current = more power = more light!


But how much thicker is that flood-light filament? Well...


Given R = ∆V / I = (ρL) / A   -->   A = (ρLI) / (∆V)
and P = I(∆V)   -->   P / ∆V = I ,
cross-sectional area A = (ρLP) / (∆V)^2.


So if both filaments have the same ρ and L, and ∆V is constant (at 120V),


Alamp = 52(ρL) / (∆V)^2
Aflood = 65(ρL) / (∆V)^2


Therefore, the flood-light filament is 1.25 times thicker than the lamp bulb filament. When we discuss filaments, we're talking about mere millimeters (or less!). So such a minuscule difference in filament thickness really impacts the brightness of a light bulb. 

FASCINATING.

FASCINATION x 2

Blog 9: Travel Voltage Converter

Once again reliving my memories of my trip to Vietnam, I now see the physics behind one of the most overlooked yet important pieces of travel equipment: the voltage converter. 

The many faces of an unsung hero

Because different nations have different power systems, the voltage that is contained in power outlets is not always the same. The voltage in Vietnamese power outlets is 220 V, whereas American power outlets run at 120 V. 

The voltage difference presents a major problem. If you plug in your American device, which is constructed to run on 120 V, into a 220 V outlet, there is a difference of 100 extra volts that flow into your device. That voltage difference, as we were warned by Mr. Brown (a trusty veteran of Vietnam travel), could cause the entire hotel to black out, and fry your device.

Now, what is more important here?

Wait - 100 V isn't very much, considering that a Van de Graaff generator can produce about 400,000 V. So how can 100 V cause such a stir?

Well, voltage is a ratio of energy to charge. The Van de Graaff may produce 400,000 V, but the ratio may be 40 joules / (1/10000) Coulomb. However, 100 V in a power outlet could mean 100,000 joules / 1000 Coulombs, which means that there is a large amount of electrons, and thus a large amount of energy. That is why 100 volts running through your device could mean doom for its circuitry. 

During our first night's stay, some idiot forgot to use a converter, so Tan My Dinh Hotel had a black-out. Though someone got stuck in the elevator, the worst part about the black-out was the absence of TV or air conditioning for an hour. Lesson learned - don't go traveling without a voltage converter!

Blog 8: ASIMO

Honda's ASIMO ("Advanced Step in Innovative MObility") humanoid robot is certainly an interesting piece of technology. While in Japan for a 12-hour layover (returning from Vietnam), our tour group had the opportunity to meet Mr. ASIMO. He greeted us with a few 'words.'

'What, is this blog late?'

"Of course not."

ASIMO was able to walk, run, use non-vocal expressions, and he could even dance. I'd say that makes him pretty human, because I definitely can't dance as well as him.

What made ASIMO incapable of ever being a human, however, was his peculiar stance: he could not stand still without having his 'knees' bent. 

"Am I not human? But I can cry..."

As it turns out, ASIMO, with all of his robotic gadgetry crammed into his back panel, has a center of mass located slightly behind his heels when he stands up straight. Therefore, the torque caused by his mass would cause him to rotate and fall over. To compensate, his designers forced him to be bent-kneed at all times in order to keep his CM inside of his support base and to protect his expensive circuitry. 

Thus, for self-preservation, ASIMO continues to be a bent-legged robot, suited for waiting tables.

Maybe next time, buddy.

Blog 7: Giant Guitar

On the East Coast college tour a year ago, I saw this enormous Les Paul sign at Reading Terminal, Pennsylvania, and I just had to take a picture of it because I love guitars.

Strings and all.

The guitar was also interesting because it rotated about the y-axis created by the neck. However, I only now understand the physics of this enormous rotating guitar. 

The guitar undergoes uniform circular motion, which means that an ant standing on one of the tuners would experience less centrifugal force than one hanging on to the widest part of the guitar body. Also, the guitar experiences torque as it rotates (there is probably a bar going across the rotational axis to turn it). However, it must take a pretty strong motor to turn this massive guitar - and it was going at a surprisingly high angular velocity - and keep it rotating for the time the Hard Rock is open. 

When I asked my friend Dylan, another guitar aficionado, he declared that the motor was powered by rock and roll, which makes perfect physics sense.

 

That guitar kind of looks like mine, too.

Blog 6: More Mr. Park Physics - Momentum

Once again, Mr. Park gives me new reasons to blog about physics. This time, I have decided to elaborate on the physics of his tennis prowess. 

Physics seems to follow him wherever he goes.

Every quarter, Mr. Park allows his Pre-Calculus Honors classes to challenge him at tennis. The rules are as follows:


1. If a student plays tennis, the game will be 1 v 1. If a student does not play tennis, then an unlimited number of students are allowed on the court against Mr. Park.
2. If the students do not play tennis, they receive a 30-love advantage over Mr. Park and can serve anywhere in the court boundaries. 
3. For every game won against Mr. Park, all PCH students receive one bonus point for the quarter.


Last quarter the students played Mr. Park for about four hours in total, and earned a total of 5 bonus points. Therefore we won one game (and thus one point) every 48 minutes spent in the hot sun. That is a really long time to spend just to earn one point. This means that Mr. Park is very good at tennis.


The reason? His serve. No mere student is capable of returning it. Why?


Let's take a look at the physics of his serve.
When Mr. Park serves the ball, the ball gains momentum. The more momentum that the ball has, the harder it is to stop the ball (and send it back).
On average, a tennis ball weighs about 0.057 kg and professional players (like Mr. Park) can serve the ball at 70 m/s. 
Thus, given p=mv, p=(0.057)(70)=3.99 kgm/s.
For comparison, a baseball pitch coming in at around 75 mph (high school pitchers) has about p=(.15)(33.5)=5.03 kgm/s of momentum. This means that returning Mr. Park's serve is actually somewhat comparable to hitting a baseball, except you don't know where the ball will land, and how deep it will land, or whether or not Mr. Park put a ton of spin on the ball. 


So that is why we cannot earn many bonus points in PCH, and that is why I cannot earn an A.

Not because we suck at tennis or anything.

Not because I suck at math or anything.

Blog 5: Physics of "Rocky"

After an exciting Homecoming week, I am finally ready to settle back into the fascinating world of physics. Looking back on Homecoming week, though, I can make many connections to physics, even after the rowdiest of celebrations. Here in this video, the ever-entertaining Mr. Park rocks out to the "Rocky" theme song:

Today's lesson in Pre-Calculus Honors: How to be awesome.

Hearing that spirited song now immediately conjures the image of Rocky Balboa climbing those 72 steps of the Philadelphia Museum of Art in intense training. However, I now understand the physics behind Rocky's training, and why it was so impressive.

After watching his ascent again, I estimate the time it took for him to climb those steps to be a little less than 7 seconds. With such a small time, sprinting with great acceleration (he had the entire city chasing after him) over a long and high distance, and a relatively large mass (probably about 100 kg), his power would be very high given the equation P= W/t = [(ma)(∆x)/t]. With such power, no wonder Rocky was so successful.

Go Rocky!

(Thanks to Mr. Park for the inspiration.)