What I've learned from Physics...

I've learned many things from Physics...However, I'd prefer not to name every single little fact...

We covered 2D Kinematics first in which we learned about mass, acceleration, velocity, time, distance, scalar and vector quantities, magnitude, gravity, and some conceptual things. For example, if an item is tossed up with a velocity of 10 m/s, at the top of its flight, the object has a velocity of 0 m/s and at the bottom it has -10m/s. Gravity on earth is ALWAYS 9.8 m/s^2--what changes in the object's flight path is velocity, not acceleration. 

Next we learned about triangles and axes. (Axes are independent by the way; what happens on the x-axis stays on the x-axis. Same for the y-axis.) This helped when we covered later units--the Break Technique does exactly what it sounds like; it breaks the diagonal up into two separate horizontal and vertical parts.

Then we covered forces and Newton's laws. The first one states that objects at motion will tend to stay in motion unless acted on by an outside, unbalanced force. Replace "in motion" with "at rest" to get the other half of the law. The first law is also known as the Law of Inertia. The second law states that acceleration of an object is directly proportional to the net force on an object and inversely proportional to the mass of the object. The third law says that for every action/force, there is an equal and opposite action/force. We also learned about Normal Force, tension, terminal velocity, frictional force, and pulleys.

Next we covered Momentum. The law of conservation states that momentum can neither be created nor destroyed; it just changes forms. Impulse is the change in momentum. And like force, the impulse experienced by two objects pushing against each other is the same.

Lastly, we covered energy, which is entirely confusing. Energy also can be neither created nor destroyed; it only changes forms. Work is not power. Power is the rate at which work is done. 

(We did not cover linear momentum...or Keplar's Laws...or some other things on the review packet...so I hope they are not on the test even though they're in the review packet...)

The picture is because after this semester is over, I can visit my uncles in LA.

エネルギ

Energy is measured in joules, which is kgm^2/s^2, or Nm. It is a scalar quantity, which means that it only has "muchness." Work is Force * Displacement; it is different from power, which is the rate at which you do work. The equation for power is Work / Time. Therefore Time is irrelevant to Work, but very much relevant to Power. Do not mistake the two. 

IfI raced my friend who weighs the same as me to Nijo Temple in the back of the photo, and she finished 2 seconds before I did, we would have done the same amount of work. However, because she finished before me, she'd be using more power than me.

Here are some equations we've learned for work...

Potential Energy (s) = 1/2kd^2

Potential Energy (g) = mgh

Kinetic Energy = 1/2mv^2

It seems relatively easy so far...But when you toss in drawings of springs, ramps, friction, and wind tunnels, everything starts to get a bit more confusing. 

Egg Drop

Recently, we had to create something that kept an egg completely safe and unharmed when it was dropped off about three and a half stories. Despite previous years' classes having a safe rate of about 50%, my class had a larger percentage safe. In fact, I believe only one or two groups had cracked eggs!

Anyway, for mine and Austin's project, we stuffed the inside of a box with various soft, cushion-y materials. The bottom of the box was lined with short, rectangular foam. On top of that, we place cylindric foam, staggering it so that it would be held in place by all the other foam cylinders. In the middle cylinder, we dug out a hold for the egg to rest in during the drop. Lastly, on top of the egg, we placed a bag of packing peanuts.

There were a lot of interesting designs, I liked the arial screw-like design by Joe and Jason. Anyway, we were really happy our egg survived. I took a really terrible video of it because I was unprepared when Austin dropped it. My finger tries to steal the show...

Crashing Cars

There are two types of collisions: elastic and inelastic. An elastic collision is a collision in which the objects involved bounce off of each other. Think of a being hit with a pillow during a pillow fight--that is an elastic collision. An inelastic collision is also known as a sticky collision. For this one, think of being hit with a snowball, or a massive ball of tape. Because both objects stick together, there is only one velocity for these collisions.

Previously we did an experiment that tested mass, velocity, and both collisions. My group personally had a lot of difficulty, but we managed to complete it. The elastic collision in which the more massive car hit the lighter car at rest was my personal favorite. It demonstrated how momentum is conserved. To make up for the lack of mass the heavier car had, the lighter car took on a faster speed.

Note: To find the velocity of the mass of an inelastic collision, the equation is as follows.

v = (p1 + p2)/(m1 + m2)

Impulse

Impulse is the change in momentum. Because impulse is the change in momentum, its symbol is a P, which stands for momentum, and a ∆ which indicates change. So ∆P represents impulse. The equation for change in momentum is: Fnet*∆T = ∆P. It can also be represented by P(o) - P.

If two objects, a rubber ball and a box, are thrown at a wall, the rubber ball will undergo a greater change in momentum than the box will. This is because the ball bounces back while the box hugs the wall and slides down. The ball bounces back towards the thrower this indicates the ball now has negative momentum. Suppose the ball, which bounces back the same speed in the opposite direction, and box are both 1 kg while the velocities are both 5 m/s to the right. The original momentum of the box is 1kg*5m/s =  5Ns. The final momentum of the box is 0Ns. The original momentum of the ball is 1kg*5kg = 5Ns. The final momentum is 1kg*-5m/s = -5Ns. Therefore, the impulse of the box is 5Ns - 0 = 5Ns, while the impulse of the ball is -5Ns - 5Ns = -10Ns.


Another thing to note: the longer the change in time is, the longer force can be applied at a low rate, as opposed to a short change in time with high force. The former is less painful than the latter. That is why it is better to land on a mattress than it is to land on cement when you jump off a high platform. (The picture is of my soft mattress that would probably not save anyone if they jumped off a high building, but would still reduce the impulse by at least a little bit.)

Linear Momentum

Momentum is mass multiplied by velocity so the SI unit is kg*m/s; there is no shorter way to write this unit. Mass is directly relational to momentum and inversely related to velocity. Therefore a fast but light ball might have the same momentum as a heavy but slow ball. In a more life-related example, if a deer from Nara, Japan takes a running start and attempts to tackle a gigantic but rather slow moving bear, the deer and bear may still have the same momentum if their m*v are the same.

Momentum is a vector because velocity is also a vector. Although there is a another sort of momentum besides linear, the other will always be specified as angular momentum. If unspecified, it is to be assumed that the material is referring to linear momentum.

(This formula is rather reminiscent of Newton's 2nd Law....)

Newton's 3rd Law

Philosophical or not, nearly everyone has heard of Newton's 3rd law:

 For every action (force) there is an equal and opposite reaction (force).

Yes, it can be applied to real life to reason that your little brother probably will plot revenge upon you for eating his ice cream, but it is mostly used for physics. That is, every time you push upon something with a force, that something pushes back on you with the same magnitude of force.

 For example, if Branson, the boy in the picture, pushed his seal plushie with a force of 10N, the seal, irregardless of being inanimate, pushes back on Branson with a force of 10N in the opposite direction. Thus, the force exerted both ways is the same. However, the accelerations of the seal and Branson would be different. This goes back to Newton's 2nd law, in which Fnet = m*a. Essentially, because Branson has a bigger mass than the plushie, he will accelerate slower than the plushie will. (Mass and acceleration are inversely related, remember?)

Forces yayyy...

The net force of an object, is the sum of all the forces acting upon it. The net force is equal to mass multiplied by acceleration. Weight, friction, and air resistance are all examples of forces. The Snorlax is not accelerating because it's net force is zero. Weight holds the object down, but the normal force of the table underneath the Snorlax, pushes it up to create a net force of zero. If a pikachu rolled a pokeball on a rough surface there would be frictional force pushing back against the force the pikachu is exerting on the pokeball. The weight plus the frictional force, plus the normal force, plus the force the pikachu is exerting on the pokeball would be the net force in this case.

Unit 4 and Forces

A force is a push or pull. It can be balanced or unbalanced. A balanced force is when two forces are acting upon an object such that the object does not accelerate because force A = to force B. Therefore there is no acceleration among balanced forces, but there can still be velocity. 

On the other hand, an unbalanced force is pretty self-explanatory... but creates an acceleration. Gravity is net (unbalanced) force. 

Inertia is the "want" of an object to stay in its current state of movement or rest.

Inertia makes sense when you think of heavy, bulky items in comparison to light, feathery objects. The heavy objects are harder to move and when they do move, they are difficult to stop once in motion. Light objects are easy to persuade to move and also easy to stop.

For example, if a vending machine were traveling at 10 mph, it would be much more difficult to stop that than something like a tennis ball.

What Happens in Vegas...

...stays in Vegas.

Similarly, what happens on the x-axis stays on the x-axis. The same goes for the y-axis. This can be summed up in the sentence, "Axes are independent."

So what does this mean?

They function without each other; the velocity on the x-axis does not affect the velocity on the y-axis.  This can be proven  in the very simple example we saw and heard in class involving two pens. Both pens were released from the same height. The difference is that one pen was just dropped while the other was projected horizontally. Both pens landed at the same time, which proves that the axes are independent of each other.

Unit 3 and Vectors

So whoever actually looks at the pictures on my blog must think I'm animal-obsessed by now. For those who care to read this, I am not, but my dogs are the easiest things to capture in motion. Anyway, this is my dog being chased.  This picture shows relative magnitude and the direction he is running. Luke is running fast enough to blur the picture. You can tell this because he is blurry. He is also running in the direction of the camera; you can tell this because his head seems larger way than the rest of his body in this picture.

This represents a vector, which shows magnitude (muchness) and direction.

(And the picture refuses to let itself be fixed. I tried.)

Velocity and Time

At the top of a building, two identical objects are released. Object A is thrown downwards, while Object B is simply dropped. Which of the two has gained more velocity? 

(Hint: Which object takes longer to reach the ground?)

This is similar to one of the questions on the practice quiz for Mr. Blake's class.

Answer: Object B gains more velocity. The longer an object takes to reach its destination, the more velocity it gains. 

It took me a while to understand this, actually. I ended up asking my genius physics friend, Robert. He explained the concept to me. While I didn't remember all of what he said, I do remember that he brought up the equation V = Vo + AT. As you can see, acceleration is multiplied by time. I think Robert said that because the equation works like that, the higher time is, the higher velocity will be.

longer time = more velocity

(And I admit that this picture has nothing to do with this blog post.)

What Goes Up...

...must come down. And when it is caught at the same level, it will have the same speed as when it was thrown up, but in the opposite direction. The progression of speed will be as follows: fast-slower-slow-stop-slow-faster-fast. Does that make sense?

As an example, I will use the rose here in my picture (because I was too lazy to take another picture). If I throw the rose up at a speed of 2 m/s and catch it at the same height, the speed will still be 2 m/s, but the direction will be different. The rose would be going 2 m/s downwards instead of upwards.

Kinematics x Doggy

Velocity is similar to speed in that they both deal with how fast something is moving; however, velocity also deals with the direction in which the thing is moving. Therefore, an object can be changing its velocity, but not its speed. For example, when my dog, pictured here, runs at a constant pace around my yard, his speed will not change. However, because my dog has to turn around and run in giant circles to avoid hitting my gates and walls, he changes his direction and therefore changes his velocity as well. In essence, direction is the only difference between speed and velocity.

Kinematics of a Fan (Impressive)

Wow. This is a breathtaking photo of my ceiling fan courtesy of my phone. Slight sarcasm aside and regardless of the quality of the picture, in photography this is called an action photo. It is categorized so because it captures motion. The blur of the blades of the fan was created because the blades were moving at a speed faster than my phone's shutter speed. This represents kinematics in physics because the fan was in motion; the blades had a speed. When fans are on, the blades travel a great distance, but they don't really go anywhere. What I mean is that the displacement is small because as far a distance as the blades travel, they never detach themselves from the fixed point in the center. (They never go flying across the room because they are attached at the center.)

Physics in the Photo

This is another photo that I took when I was in photography. It is one that I am especially fond of because it looks rather whimsical and maybe almost nostalgic. This represents physics because of what my friend, Maile, is unable to do--that is, she cannot fly with an umbrella. Unfortunately, she is no Mary Poppins or a magical being with no mass. Because of the pull of gravity on her, she cannot float away under the umbrella like a smaller creature might be able to. However, because of the gravitational pull on her, she is able to do everyday things like running, jumping, kicking, and rolling. 

Introduction...

I'm Marisa. I enjoy doing things like playing tennis, making jewelry, and baking along with a few other things. Although I've gotten good grades in my past science courses in high school, they were during the summer and the lowest level. I'd like to think I'm not terrible with science, however, because I was admitted into the PSTP program at Temple University (although I quit after one year). Currently, I am in Honors Pre-Calc. From all of my classes, I hope to learn more of anything they can possibly teach me. The picture is of Luke, one of the two dogs that I keep. I took this photo for the photography class I took last year. It was a little challenging to get him to look at the camera, but I managed to get his attention by gifting him a dog treat. This photo represents the fact that I like creating things--anything.