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Archive for October, 2007

Happy Halloween!!!

Halloween-1.gif picture by xtaintedwatersx

I’m really starting to enjoy writing this blog you know…it’s nice knowing that I have some weekly readers from all over the world being inoculated with physics!

Putting the mawkish stuff aside, I actually for once had a semi-relaxing weekend! Even though Fall Break was a measly one day, I had a wonderful time at Ala Moana with a friend. And of course, since it was a holiday, any mediocre food just wouldn’t do! Which is why we went to Cold Stone Creamery for ice cream creations!!!  (after savoring hot wings from KFC)

Now my friend, who is uber-smart, knows that I’m taking Physics right now. Having been through that phase of life herself, she asked me, “So, have you guys studied Newton’s Law of Cooling yet?”

To which I dumbly shook my head and with much astonishment answered with a question of my own: “There’s a Law of Cooling?!”

She laughed at my dearth of physicsy wisdom and proceeded to explain the following: Newton’s Law of Cooling states that the rate of change of heat loss of an object is proportional to the difference between the ambient temperature and the object’s own temperature.

Eq: Q=h x A(To-Ta)                                                               ColdStoneChocalateDevotion.jpg picture by xtaintedwatersx

Q- amount of heat transfer

h- heat transfer coefficient

A- surface area of object

To- Temperature of object

Ta- Temerature of surroundings

Then she started talking about derivatives so I gave up trying to understand any more…but obviously Newton’s Law of Cooling was present and heat was being transferred because my Chocolate DevotionTM was slowly melting.

Supposedly, with this law and some more equations, you can even calculate the time of death of an animal if given the initial and final temperatures of a corpse and the temperature of the room.  Scary, especially with Halloween on the way…

With the malignant glares we got from a I’m-on-a-diet-so-don’t-you-dare-eat-that-ambrosial-food-full-of-calories-in-front-of-my-face-and-look-so-happy person spooning yogurt nearby, Newton’s Law of Cooling could have come in handy. 

Luckily it didn’t. ; K

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Hello!  I wrote this post earlier than usual because this weekend is a hectic one with the psat…

Today we were playing dodgeball in my PE class.  I got “out” pretty early in one round due to my absolute lack of athletic skills.  So I was just sitting there on the floor of the wrestling room thinking about all the sweat and other bodily fluids that must have covered the surface at some point in time when…  I noticed a black squishy “Rhinoskin” ball at rest.  Soon, a blue ball of equal mass rolled towards it and there was an amazing occurence. 

Right there in front of me, the balls collided, sending the black one off at an angle.  The blue ball kept moving but at a different velocity and in a direction that looked perpendicular to the direction of the black ball (characteristic of elastic collisions).  Clearly, this could have represented a game of pool in which a cue ball hits a target ball in a elastic collision.  The collision is not head on so the target ball travels in the direction of the line connecting the centers of the two balls when they are next to each other and not all kinetic energy is transferred.  The system’s overall momentum and kinetic energy would have been conserved.  Of course, I would have had many calculations for you if I had known the initial velocity of the blue ball.

Awesome, yes?  But the environment definitely did not include a pool table…soon the “playing” got more intense and I had to move out of the war zone to avoid a major concussion.  I’d hate to make myself the victim of such a vicious, bloodthirsty beast.

Blue…     Hits    Black!!!

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Elevator Physics

Ghostly Elevator!

My physics experience of the week was the hackneyed up and down an elevator one.  I ride the elevator in my apartment building everyday but this particular day was special.  My grandfather, on an around the world trip, arrived in Hawaii as his last stop and came to our place.  

As we went up the elevator this time, I had the sudden impulse (not in the physics sense) to explain the present physics of the situation.  From a position of rest, the elevator accelerated upwards.  Since Fnet=ma and the normal force was much larger than weight (mg), I felt heavy and bogged down.  During the long elevator ride, I explained the concept to my family members in Chinglish (an exotic mixture of Mandarin Chinese & English) since my grandfather can’t understand my English when I’m supposedly talking too fast.  It felt very good to be breaking through a language barrier!  My experience wasn’t so clichéd after all!  ^ ^ 

An hour later, on the way down, the net force was now downwards.  I explained how that since weight was now greater than the normal force, we felt much lighter.  I think that my parents and grandfather really understood what I was saying…either that or they were just oohing and nodding to humor me.  On the other hand, my brother completely ignored me and started jumping up and down which made the elevator feel shaky.  Afterwards, he would also throw a projectile motion french fry at me by “pure accident”…twice…aren’t siblings just bundles of joy?

The next day, my grandfather went back to Shanghai.  Hopefully, he’ll spread the word about the wonders of physics!  He promised me he would at least try and act as my ambassador…since there’s an elevator in his apartment building too.  He also gave me 1,000 rmb.  Maybe I could use the money and start a ‘physics of an elevator’ awareness program!  : )

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Work, Physics, & Soccer

Yay for the long weekend!  Not so yay for the increased homework load and excessive number of tests next week!

On Saturday I got pathetically lost.  No need to get into details but I still blame a certain police officer and his completely erroneous instructions.  Combined with my horrible sense of direction, it was…just bad.  Very bad.

So I basically end up circling a 500-acre park.  The only good things I got out of this two miles long detour were beautiful observations of the physics universe.  After all, it was hard to ignore the bajillions of tiny soccer players screaming and running.  And of course, the kicking of the muddy soccer ball.  (I did not have a camera at that moment, so here are substitute pictures.)

Beanie Soccer BallBeanie Soccer Ball 2Beanie Soccer Ball 3

One soccer ball had no kinetic energy, but not for long.  A youngster soon ran up to it and kicked it hard towards the goal.  The force exerted by her foot accelerated the ball.  Expressed in a simple work-kinetic theorem equation, the work done by her foot on the ball should have been equal to the change of kinetic energy of the ball.  However, to be more accurate, we’d have to account for friction between the ground and the soccer ball slowing it down too.

And did I mention that during this whole time, I was carrying my ponderous violin case with me? But since the force I was exerting (up) was perpendicular to the displacement (forward), a physicist would have concluded that I was not actually doing any work.  How sad.

Thankfully, the rest of Saturday was rather uneventful.  I did pretty much nothing except go and check out Punahou’s “canteen” for the Class of 2013.  Lots and lots of food…and no one even noticed me. : )

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