The eeennnd !! ! (or the beginning?)

What is physics? It is the study of EVERYTHING from the universe, to light, to sound, to the mechanics of the human body, to motion. Physics incorporates big ideas from the other branches of science: chemistry and biology, and then explains why and how things are the way they are in our world/universe. It's all very fascinating indeed !!

I enjoyed the class a lot more than I thought I would because I feel like I learned a good amount of basic physic ideas. I usually have a hard time with all this type of material (with the equations and logic stuff), but because this was my only focus (for school), I was able to understand and keep up. I remember taking astronomy and asking basic physics questions, to which my teacher would tell me to "take physics!" if I was so interested. Although I'm usually not that interested in math, because it was all applied, and had meaning behind all the equations, it was all very fascinating, which made me actually want to learn.

My favorite part of the whole 6 weeks was definitely this past week when we covered light. I really wish we could go further into it, but I understand that 6 weeks would not be enough time to go any further. Because I now know the basic ideas of physics, I would like to learn more about other concepts such as the theory of relativity (and the speed of light), and more about how light works, and much more !

Overall I'm glad i took 6 weeks out of my summer to learn ! 

Unit 10: light refraction

  

The image above represents what happen when light refracts (or bends). The shape in the middle would be the lens, and the smaller cat on the left is the object, and the large cat on the right is the real image. The horizon line is the optic axis, where the two focal points sit. The green ray is the parallel ray, and travels from the object parallel to the optic axis then through the lens, and bends through the focal point on to the other side. The red ray, or the focal ray, travels from the object through the focal point on the object side, through the lens and then parallel to the optic axis.  The blue ray is the central ray and travels from the object through the center of the lens, and then continues without bending. t a d a

Unit 10 Light CONTINUED

Today, we learned about color mixing !! woo!
Everyone learns how to mix colors, but the color wheel for pigments is completely different from the color wheel for lights. The primary colors for pigments are, red (or magenta), yellow, and blue (or cyan), but the primary colors for light are red, green, and blue. So in the picture to the left, there are two shadows because there are two light sources ( blue and green). On one side, the shadow is blue, because this means that Mr. Blake is blocking the green light, so there is an absence of green light, and vice versa!

Unit 10: Light Behaviour !

So there are two objects above, with a light beam shining at them. The first object, the fishbowl, is a transparent object, so the light can go through it. The other object, the dead fish, is an opaque object, so the light cannot go through it. Light acts as an electromagnetic wave, and does not need a medium to travel, which is why it is able to travel through air ! (and water, and empty space, etc)

Unit 9- continued

Mr. Mcphee is going down a little hill. He's freaking out before he even takes off, and emits a gross screech sending out these imaginary red sound waves through the air. So these sound waves are moving at a constant speed of 340 m/s through the air. As Mr. Mcphee goes down the hill, the sound waves now look a little different. They are all closer together in the direction that Mr. Mcphee is moving, but are further apart to his left.
This is the doppler effect! exciiting !!

Unit 9: Waves

Today !
we learned about waves~~~~~~
So what exactly is a wave?
Well a vibration, is more of a "wiggle in time", while a wave is a "wiggle in time" and in space! It is basically this energy that moves through space and time in an undulating motion.
So how long is one wave length?

ta da! So from the first point to the second point is one wavelength. The wave started at point A and ended up in the same spot at point B (on the horizon line). 

So lets look at a certain situation to explain constructive interference (one of the interferences I can actually demonstrate with this wave and penguin example). So penguin guy is surfin and he notices a wave of the exact same size is coming towards him in the opposite direction. What will happen when the two waves collide?

The two waves collide and make a super massive one! But it doesnt last for long.. The two individual waves will then continue to go their separate ways, never meeting again. : ' (

End of quarter: Water Bottle Rocket Analysis

We made sure to include a heavy top, four fins placed evenly toward the bottom, a parachute, and a cone surrounding the top. The fins were the most consistent, until one of them broke off at the end. We had the most trouble with the parachute deploying correctly. We adjusted our parachute designs a few times. The first time we made the parachute a little more circular and even, as the first parachute design was not as even. Then we launched it, and had some issues with the bottle leaking, and the parachute just not deploying. Then we removed a rock from the top to try and lighten it, in hopes of the parachute deploying. When it did deploy, it was tangled, so it didn't work so well. So we retried and folded up the parachute in a way so that it didn't get as tangled. After a few more tries, it deployed, but it got tangled up with the cone. On our last try, the rocket was pretty worn down, and fell apart in the air. I believe in order to make it work, we needed a larger parachute and maybe even longer strings.

 

In the beginning we were filling up the bottle with too much water, so in our final tries, we filled it up with a little less than half of the bottle. From what I remember I believe the psi was about 45 at one of our launches.

 

I learned that the center of gravity of the rocket has to be pretty well centered so that the rocket won't tip over, and we were able to accomplish that pretty well. Also, having four fins that were an equal distance from each other also kept the rocket balanced. Although there were many frustrating points, it was a pretty fun experiment. I definitely had the best time decorating/creating the rocket aha. c:

Water Bottle Rockets !!!!

Capri and I made our rocket today out of some simple materials. We used some posterboard, duct tape, string, an extra cut up bottle top, rocks, a trash bag, and more tape. I made the fins out of posterboard, and shaped them to look like surfboard skegs. I was just experimenting with the shape of the fins, trying out something a little different than the generic triangular shape. I wasn't sure how the shape would affect the bottle, but I made sure the fins stayed relatively small and closer to the bottom of the rocket, so it would be stable during the launch. I also taped up the fins with clear tape to make sure the water wouldn't destroy them after one or two launches. I taped the fins onto the bottle (an equal distance away from each other) with duct tape to make sure they would stay attached to the bottle.

Capri then made the parachute out of a trashbag, and we taped strung some string through it and taped it onto the top of the bottle. We then made a weighted top out of a cut out top of another bottle. Inside the top, we taped some rocks and string to add about 50 grams to the top, so the bottle would not tip.
We used about 1 2/3 liters of water to launch for the first two trials. The first trial worked out really well, but the parachute didn't deploy, but it did stay in the air for about 5 seconds!

Unit 8 continued

Let's say that there are two kids racing. Rai is about 40 kg, and Janelle is about 45 kg and both complete a short race of about 5 meters in 3 seconds. So we want to find out the power that each individual kid can develop during this race. Power, or the rate at which work is done, is calculated by using the equation, change in energy/ change in time and is measured in watts. So first we must find work done by each kid. To find work we use the equation, force x distance traveled. So force is mass x gravity, and the distance for both of them is 5 meters. Rai gets about 1960 Joules of work done, while Janelle gets about 2205 Joules of work done. So in the end, Rai develops 653.3 watts of power, while Janelle develops about 735 watts of power.

Now let's say Rai decides to race with a lemon suit on, which adds 7 kg to her mass. Now who will develop more power in the end if the other variables are unchanged? So Rai would get about 2303 Joules of work done, and develops 767.7 watts of power. So this shows that the greater the mass, the more power it can develop! 

Unit 8

So there's this fairy, about 0.1 kg and he's going about doing his business, flying around looking for some sweet flower nectar. While he's flying, he's going at about 3 m/s, so what would his kinetic energy be? Kinetic energy is the energy of motion, so to solve this, we would use the equation, 1/2 x mass x (velocity)^2 to get a number of Joules. So we would get a kinetic energy of, 0.45 joules from 1/2(0.1 kg)(3)^2.

Now let's say this fairy dude finally finds some sweet nectar in a flower about 1 m above the ground. In order to obtain this nectar, he has to stop for a little while and hang out (at rest). So what would his potential energy be at this point? So to find potential (or gravitational) energy, we would use the equation, PE= mass x acceleration of gravity x change in height. So this fairy's potential energy at this point would be 0.98 joules from (0.1 kg)(9.8)(1)

Egg drop write up

We made our egg capsule out of plastic cups, string, ziploc bags, and some paper napkins. We cut slits going half way up the cup in order to increase air resistance, and to create a softer landing instead of a "bouncy" landing. The latticed string was created as a sort of nest for the egg, elevated high enough so the egg would never touch the ground during impact. The nest was slightly drooping so the egg wouldn't bounce up but instead would fall into the string nest. Then we added the napkin on top of the string nest to make sure the egg wouldn't fall through the cracks, and we also made a little belt out of another napkin so the egg wouldn't bounce out of capsule during impact. The Ziploc bags surrounding it were there for extra protection just in case the capsule tipped over, or the napkin belt was not enough to keep the egg from falling out.

 

So our capsule worked out really well for a few reasons. Our cups had two very important roles in preventing the egg from breaking. One, they increased air resistance, so the terminal velocity was never at a high speed, and two, they helped absorb force during impact. Because we used light material to build our capsule, there was never any great change in momentum. So momentum (p) = mass x velocity, and because both the mass and the velocity of the capsule were on the smaller side, the momentum of the capsule never reached a very fast speed. So because Force = change in momentum (p)/ change in time, the force the entire capsule felt was not as much as it would be if the capsule was larger, or if the capsule was not built with a good way of resisting air during its fall.  So we decreased the amount of force the capsule and egg felt by increasing air resistance (which decreases velocity), and by making the capsule pretty lightweight (which decreases the mass).

We also made sure that the egg was rested right in the center of the entire capsule in order to prevent it from tipping. But in the case that it did tip, the ziploc bags should have created some cushion for the egg, but it definitely would not work nearly as well. The ziploc bags were also helpful because they prevented the egg from falling out during impact. Newton's law of inertia states that, "an object in motion will tend to stay in motion unless acted upon by an outside unbalanced force". So while the egg was dropping, it was being pulled down by gravity and being pushed upon by friction (from air resistance). So during its fall, the egg was moving down towards the floor because the force of gravity was greater than the force of friction, but during impact the egg suddenly felt a great amount of force from hitting the solid ground. The egg then wanted to move in an upwards direction because of the sudden and strong force from the impact, so the ziploc bags prevented the egg from doing so by blocking its path.  Then it finally was at rest, which meant the force of its own weight and the force of gravity were balanced.

unit 7 continued

So there are two guys that decide to jump of a very high place at the same time, but guy #1 jumps and lands into a huge air mattress, while guy #2 lands on cement. So why exactly does the guy who lands on the air mattress survive?

The reason is because of the amount of time each guy gets to collide with an object. Lets say guy #1 lands on the air mattress and the entire collision lasts about 1 second, while guy #2's collision lasts about 0.01 second. Within this amount of time both of their velocities are decreasing, but guy #1's velocity is decreasing at a more steady rate, while guy #2's velocity is decreasing in an instant. Guy #2 feels much more force because his time of impulse is much less that guy #1. Impulse is the average force upon the object multiplied by the force acting on the object, and is also the change in momentum of the object. 

unit 7

So there's this dog cat super hero type thing (which is about 20 kg) and it is going through the air at about 30 m/s. It's velocity stays constant, and of course so does its mass. So according to many, the momentum of a system should always be conserved. The equation for momentum (p) is p=mass x velocity. So if this thing has an initial momentum of 60 m/s, it should also have a final momentum of 60 m/s. The momentum stays the same throughout the movement, because the mass and velocity of the system also stay the same. So there it is, momentum of a system is always conserved!!!