# Blog DavidStack

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## Final Blog Post

Well this is kind of bittersweet, finally being done with blog posts but also realizing that high school is completely over, as is Physics C with a fantastic teacher. I've learned so much during the year, from angular analogs to retarding forces to induction to the sheer brilliance of Walter Lewin's ability to draw a dotted line; it's been quite a year. I've appreciated this blog posts as much as I've hated them, mostly because they forced me to truly learn the stuff that I write about. And n

## Hot Rod

Hot Rod, arguably the greatest movie ever created, actually has quite a bit of physics incorported into it. The part I will focus on is when Rod fails miserably to jump the local pool. Barely making it halfway, Rod slowly spins forward while in the air and lands face first, bike and all, into the pool. His demise results from two things - lack of kinetic energy and conservation of angular momentum. While he did have a ramp leading up to the jump, it was not nearly big enough to clear the poo

## Why is it Easier to Catch a Ball With Two Hands Instead of One?

As I go off to Tufts University in the fall, one of the things that I'm looking most forward to is joining the qudditch team, where I will be a chaser. One of the tuft-est (see what I did there?) things about being a chaser is that one hand has to hold the broom while you run, meaning that you have to catch the ball with solely the other hand. This is difficult for two reasons: 1) The force felt from the ball is directed onto one hand instead of two, so the force is spead across a smaller plan

## 3 Things I Wish I had Known Prior to the AP

1) Don't worry about the time, it will just make you work slower. 2) If Mr. Fullerton says it's going to be on the AP, it's probably going to be on the AP. 3) Since the AP changes every year, test taking strategies can often come in handy more than trying to hammer in every single thing we ever learned in the entire year.

## The REAL Physics of Dropping a Ball

So apparently there's more to dropping a ball than just gravity... who would have thought?! Well, for starters, when the ball is above the ground it has potential energy, due to the equation U = mgh. (See? Gravity is key!) As the ball comes closer and closer to the ground though, that potential energy is steadily converted to kinetic energy in the form of velocity (k = .5mv^2). Since m is in both equations, the mass of the object does not affect how fast the ball falls nor the time it takes

Gravity.

## The Physics of Punching Something

There are a few things that come into the physics of punching something. First off, impulse plays a huge role in punching somehting. Obviously as you punch something such as a wall or a person you will experience an impulse as you have a change in momentum. Therefore the thing that you are punching will feel the force of the punch as well as the impulse delivered from the punch. Due to Newton's second law you, the puncher, will also feel a force driving backwards in your direction as every react

## More Kerbal Space Program

There's more to the knowledge I've gained from the Kerbal Space Program. First of all I couldn't get the screen shot to work; I guess the F1 key doesn't like me. And yes, I did just use a semi-colon outside of English class. But another very important thing I've learned through the Kerbal Space Program is how to correctly get a lot of power to your rocket. While I previously thought that either putting one engine at the bottom of stack of fuel tanks (the engine doesn't have enough power to l

## Why Does Skin Get Pruney in the Tub?

After spending about two hours in a hot tub the other night and therefore having excessively pruney hands, the question that I've always been curious about came to mind: why does our skin get pruney when it's been under water for a long time? I looked up some things, and discovered that at first, scientists believed that it was simply due to the different layers of skin we have. The outermost layer of the outermost layer of our skin has cells that are filled with keratin, a protein that keeps y

## Bottle Rocket

To add to the benefits of the Kerbal space program listed in the previous post, it helped us with the bottle rocket mostly in terms of simplicity. Instead of trying to make a giant rocket with parachutes or other complicated things, we decided to go with a simple rocket because we learned the importance of aerodynamics and weight balance through the Kerbal space program. My group realized that all we really needed was the two liter bottle, fins, a nose cone, and some weight on the top of the roc

## Kerbal Project

After spending quite some time with the Kerbal project, I am starting to understand how the program works. Building the biggest rocket possible doesn't really work; you need a balance between fuel level and weight, aerodynamics, the necessary seperators and parachutes, and a knowledge of when to hold off on burning fuel, the SAS, and other things like that. Thus, our first couple launches were not as successful as we would have hoped, but as we learned to decrease the drag force by improving the

## Summing up the Quarter

As my last blog post of the quarter, I think the only reasonable thing to do is get sentimental (at least as sentimental as you can in a physics blog post) and think of the ups and downs of this quarter. This quarter was mostly independent units, which was good in the fact that it helped prepare us for college but also made me realize that I need to change a lot of my study habits - or lack there of. I also have discovered that E&M comes a lot less naturally than mechanics did, so studying

## Einstein's Hair

Although Albert Einstein's mess of hair was most likely due to the fact that he rarely slept well because of the equations constantly rattling through his brain and that he really didn't care what he looked like since he was too busy making history, electricity also plays into effect. Due to the likely rolling around that Einstein did at night, his hair felt a lot of friction from his pillow case and the sheets on the bed. This frictional force led to the passing of electrons from the shee

## Magnetism Independent Unit

Reiterating Charlie's most recent blog post, this independent unit has certainly seemed more difficult conceptually than the previous independent unit. As soon as I thought I understood something in the unit, another curve ball was thrown at me. Luckily, I discovered that Ampere's law and the Bio-Savart law are extremely helpful and applicable in this unit, and the right hand rules and simple force equations (like F=q(v x and F = I(B x L)) are easier this year because of the practice we had w

## Stationary Bike Exercise

Looking at the stationary bike that my dad bought for my mom for too much money, I realized that all these bikes do is take a normal bike and add friction to it in order to give the feeling like you are actually riding a bike. The friction of some material on the bike tire requires work to overcome it, and since W=Fd, the work required is the frictional force times the distance traveled, so you burn however many calories the work you did is equivalent to. Therefore, you can create one of the m

## The Accuracy of Mario Tennis

Although I personally believe that the Nintendo 64 is the greatest game system ever, playing Mario Tennis and my understanding of physics has led me to realize that a big reason why "better" game systems have been created is the lack of realism in the physics world in games such as Mario Tennis. The game creators didn't exactly take momentum into account given the fact that the ball is only hit with 4 speeds with 4 shots - a top spin, a slice, a lob, and a smash. In the real game of tennis, pl

## Mind Teaser

In my computers class we looked up mind teasers on mindcipher.com in order to improve our problem solving abilities, but problem solving is certainly applicable to physics and this question was relatively easy but got your brain working a little bit: You need to tell time for 30 seconds but all you have is a non homogenous rope (some parts burn faster than others) that you know burns for 60 seconds and a match. How do you tell time for 30 seconds? And if that one is too easy: It's said tha

## Tennis Serve

I recently played a very poor serving tennis match and sit here thinking about why my serve was and often is so inconsistent, realizing that it comes mostly from my toss. The racket should contact the ball when the hitting arm is fully extended, but I often toss the ball short and contact the ball while my arm is still bent. By hitting the ball at the highest possible point, I maximize power and accuracy - the ball is at its maximum potential energy so more kinetic energy results when it is co

## My Cookie Problem

Alright Charlie, I'm writing a cookie problem just for you. You might need to get the cookie from Liz, but I figured I'd write one since you said there haven't been enough. And continuing with the Disney theme, here goes: Mulan is curious about how current and magnetic field interact, so she inserts her charge filled sword (which temporarily acts like a wire) of length 1 m into a magnetic field of 2 T in the postitive i direction, creating a force a 2.5 N in the positive k direction. 1) W

## Muscle Memory

The brain is an incredible thing and is refered to as the world's smartest computer for a reason. I've recently grown to love muscle memory as it helped me greatly in performing in a musical this past weekend. Even though I would be in the middle of a dance number and completely forget the next part of the dance, my body would do the moves for me without me even thinking about it. This is because of muscle memory, as our bodies build neural pathways after doing a certain activity over and ove

## Ears Popping on a Plane

Many people do not enjoy plane rides because of the uncomfortable feeling of their ears popping as the plane rises. This has to do with air pressure, a concept that is not really covered in AP-C Physics but we did deal with last year and is certainly important in understanding the general physics around us. As the airplane increases in altitude, the air becomes less dense (since less air is being pushed down by gravity), leading to a decrease in air pressure. Because of this, the air trapped

## 3 Ups and 3 Downs of Physics C at the Midterm

So, we've lasted half the year in Physics, and what better time than now to discuss how I'm feeling about this class? Ups: 1) Physics C and BC Calc go well together. As I learn more in one class, it helps me understand something better in the other class. 2) It's interesting to learn more real world physics, such as air drag and taking friction into account, instead of learning the mechanics of a perfect world that doesn't exist. 3) Doing the same topics as last year, like momentum and ener

## Making Equation Dumps Easier

I have always failed at writing down 50 equations in 4 minutes, both last year and this year, and I was never really sure why because I do know a good deal of equations. But as I think about it, I usually try to think of every little equation - getting me flustered and slowing me down - instead of focusing on the general equations that can help me figure out other equations. So, here's a simplified equation dump of equations that can lead you to most any equation we've learned in mechanics. F

## Feeding the 5000

In the famous Bible story of feeding the 5000, Jesus and his 12 disciples feed 5000 men with 5 loaves of bread and 2 fish. But, the 5000 only counts the men, and since these people have been following Jesus for over 2 days, it can be assumed that they are with their families. On average, we'll say that each man has a wife and two kids, speaking that some of the men weren't married and some of the men had much larger families. That means that this story is actually the feeding of the 20000.

## The Physics of Test Taking

After not performing as well on the practice physics test as I would have hoped, I began to think about the physics of test taking, mainly using energy. We've learned that kinetic energy = .5mv^2 and that potential energy = mgh. In this instance, m = the question number, v = the speed that I answer questions, g = how easy the test is (the greater g is, the easier the test is), and h = my confidence. Therefore, my potential energy at the beginning before I take the test is converted to kinetic

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