Matthew 6:2

"Thus, when you give to the needy, sound no trumpet before you, as the hypocrites do in the synagogues and in the streets, that they may be praised by others. Truly, I say to you, they have received their reward".

Despite what this verse says, I will tell a story I have never told:

It was the first week of school: Thursday, 6th of August, 2015. Mum needed to pick up brother so she dropped me off at the overpass to walk home. It was about 4:00pm; cars rushed beneath the overpass while it was deserted up top, except for one beggar.

My family does not do much giving. Dad is all talk and no action. He is the greatest preacher of hunger, war, and global warming, rambling on and on at the dinner table, yet the most gluttonous, prejudiced, and wasteful of us all. Mum is more silent on the matter of poverty, since she does not have a career of her own. I have never seen my parents give. When we passed by beggars, dad tugs me along with words of pity while holding onto his "you win or you lose" philosophy.

Before the day I walked that overpass, I used to ponder. If my parents are not around to restrain me, what will I do for these unfortunate people? Will I give heartily as I always wanted to? Or will I walk on by like my parents did? More still, what if the money is of my own labour and pain? It is easy to give something that is not mine, but will I be able to give away money of my own?

So it was time to find out.

I stopped three meters from him and considered how much I should give. Then I snapped to my senses and asked myself: why am I withholding? Somebody is in need here! I rummaged my backpack for every note and coin there is. Surely I must have something, and after having searched my bag inside out and upside down, I confirmed that I only had one hundred baht.

Call me stupid, or gullible, but if anyone is willing to sit all day on a dirty overpass for a meager donation, I say that person is desperate enough to receive some help. His right hand was a stump. He held up to his forehead and I put the hundred into his cup. Then I left the overpass.

That ought to have settled my unease, having proven myself capable. But on my way home I just got upset. All I could think was "I only had one hundred baht". If only I had more to give. Why did I not have more to give? What did I spend it on? Nothing, really. I spend forty baht a day for lunch at school, and that is all.

The very next day I stopped having lunch. At least that is what I can do as a student. And as far as health goes, it has not killed me.

At home we work by a "when you need more" basis. Mum always gives me more than I need, two hundred baht a week and one thousand baht for trips. I tell her honestly that I still have money, but she stuffs it in my hand anyways, and I usually end up returning them all at the end of the year. But this time I add all the money to an envelope written "Yi Ting physics" (that envelope is another story to itself. A couple months ago I donated a total of 1,500 to help the Nepalese earthquake recovery 2015 from my talent show and science fair prizes).

By November I had accumulated a little over five thousand baht. When Habitat for Humanity came around, I did not withhold. I gave the whole envelope away. In December when the donation for Northern Thai hill tribes came around, I did not withhold and gave my one thousand.

It was the first week of semester two: Wednesday, 6th of January, 2016. Mum needed to pick up brother so she dropped me off at the overpass to walk home. It was about 4:00pm; cars rushed beneath the overpass while it was deserted up top, except for one beggar.

It had been exactly five months since, and he is still there. I did not withhold and gave my two thousand baht.

So I thought of this story because of the recent "Asia Cold Snap" (East Asia Cold Wave January 2016). It is a real thing. Having lived in the tropics all our lives, the cold was utterly unbearable. Temperatures can go as low as fifteen degrees Celsius on that open-air overpass. I hope the two thousand helped him through.

And never mind that I lost my "reward" telling this story, because it is more important that you know. It is possible to give, even when you think you have nothing to give. I have a serious lack of "practical smarts" but over the course of one year, I gave away a total of 10,000 baht. That is a lot, especially for a jobless, not-so-street-savvy seventeen year old.

You have the power to give. You do.

Fluid Mechanics

Prerequisite: physics 1, algebra 2

All things "flowable" are fluids, which may be liquids, gases, plasmas, ion soups.. but for now, liquids and gases. Specific gravity is the ratio of two substances' densities, which comes in handy with buoyancy.

One main property that fluid mechanics considers is pressure. Here are two laws of fluid statics, regarding pressure of stationary fluid on an object:

The first one is quite understandable, since pressures need to be uniform in order for fluids to be stationary. The second one is somewhat confusing, but the logic is that since nothing is moving, the net force must be zero. Backwards reasoning. Sorry for the misleading picture, here is a better one:

There are many explanations out there from torque to average force, but my understanding is this: force is acceleration times mass, so if a fluid exerts a diagonal force as shown above, the fluid mass is accelerating with a y component and therefore moving. In order for the fluid to not be moving, it can only accelerate horizontally against the rigid bottle.

A more detailed formula for pressure can be derived as follows:

P = F / A
    = (mg) / A
    = (DV)g / A
    = D(l*w*h)g / (l*w)
    = Dhg
    = Dgh

This formula is for incompressible fluids, in other words, fluids that have the same density at any depth. For compressible fluids, ∆P = Dg∆h.

 Another common formula is this:

Atmospheric pressure is obviously pressure due to the atmosphere. Absolute pressure is the pressure inside a container regardless of the outside pressure. Gauge pressure is in a sense the "net pressure".

But I rather like to think of it as P(atm) - P(abs) = P(g), in which the pressure balance between the outside and inside determines the "apparent pressure" P(g). Dunno. Makes more intuitive sense to me.

Pascal's Principle is applied in the hydraulic lift in which since the pressure is the same at both ends, the out force increases with a maximized area so that the pressures match. The increased force can then be used to lift objects.

In terms of work, the in force is smaller but needs to cover a greater distance, in order for the greater out force to cover a short distance. No glitches, hacks, nor dirty tricks. Just physics.

Another property that fluid mechanics studies is buoyancy, the ability of an object to float. By Archimedes' Principle, an object's buoyant force is the weight of displaced fluid. If you divide constant g from both sides, you have D(fluid)V(displacement) = DV of object.

In fluid dynamics, flow rate can be expressed in mass over time, and if density does not vary, volume over time. The volume rate is easier to visualize while the mass rate uses density to convert volume units into mass units.

And here, Bernoulli's Principle: pressure is inversely proportional to pressure. I like to think of it as driving, or traffic. The cars are mashed up together in the slow lane but widely spaced out in the fast lane. Planes can fly because the bumps in their wings cause air to flow at a greater velocity over the wing than under, so the pressure is greater under than over, then lift off~ And there, the equation is derived by setting work and ∆PE equal to ∆KE.

So there, the basics of fluid mechanics~

Proverbs 17:3

"The crucible is for silver, and the furnace is for gold,
and the Lord tests hearts"

Many things are going to happen this year. For the first half, there is the extra Calculus BC and Physics 2 AP exams that I need to self study. As of now I already dashed through fluid mechanics, sequences, L'Hôpital's rule, and improper integrals within two weeks. Burn, burn, burn!

Questioning my choices too. Life can be so easy if I pursued humanities as my profession. I guess easy topics have no appeal to me. Sciences are more gruelling, but the elegance of the universe's ways is far more aesthetic than all the humanities. Humanities are earthly, while sciences are transcendental. So this is why.

The burning is not so much in making time for studies, but making time for God. The test is not about whether I can retain my sanity, but whether I can keep God a part of my life. To be honest, I almost canceled this post to do more studying. But hey, priorities~

It is very tempting to take credit for myself, which is why there is the push and pull of success and failure. Hopefully by the end I will remember how I got there. As I have learned last month, no temptation is too great to overcome. I can combat the weakness of my flesh and humble myself. This is another test unto itself. The way is not so simple, but I will not be alone~

For the second half of this year and onwards, I will not be in Thailand. For sure. I have not applied for any Thai universities so it will be a whirl leaving my home of (by then) eighteen years. Living with my parents is a sweet little haven, a nice and protected bubble. Whereas being alone out there, no one will be around to rein me in. What I do is up to me. The Lord tests hearts.

But until then, these APs. Burn away, honey.