Reflection on Physics - the end

What is physics?

Physics is science dealing with energy and motion that relates to real life examples and occurrences. Physics is everywhere in our world, from the sky to the ground, and how to get there in between. Physics is the explanation for nature, and how our universe works.

What did you learn from this class?

From this class, I gained so much knowledge. As there were times when I wanted to break my pencil in half and run around the quad, there were equally, if not more moments where I was laughing nonstop. This class was so compressed, I was worried that I would get behind and perform poorly. However, with help from my friends, I got help when I needed it. Mr. Blake would always patiently listen to my questions, and help me figure out what I didn't understand. Unfathomable concepts became basics to my physics brain. Before the course, I didn't expect anything close to the summer I've had.

What did you like about the class?
I absolutely loved how each concept was relative to something in our daily lives. Doing our homework was pretty easy, because we could identify the concepts from class. Mr. Blake gave us such clear examples and made sure we understood each idea before we left for home.

What could be modified to improve on the class?
I think some labs could've been modified or replaced by a lab more related to the unit idea.

Commentary/Feedback?
I had a lot of fun and learned so much, thank you Mr. Blake!!

not as it appears - unit 10

Refraction is the changing of wave speeds due to changes in mediums. Today, we did many demos and worksheet problems to learn how these certain refractions look in real life. The index of refraction is represented with the letter n. n = c/v, which is the speed of light in a vacuum (3 x 10 ^8 m/s), divided by the speed of light in the medium. Some indexes of refractions we learned, are air (1), water (1.33), glass (1.5) and diamonds (2.42). If we put this in the c/v = n equation, you can get each speed of light in the medium.
Refraction is dependent on the medium, where if there is change in 2 media, bending will occur. Snell's law is an equation that can be applied to refraction. With this equation, we can find the angle or the index of refraction. The critical angle happens when there is change in media. All critical angles are relative to the normal.

when will my reflection show? - unit 10

Today, we did a lot about mirrors, colors, shadows and reflection. There are two types of reflections: specular and diffuse. A specular reflection is a smooth surface relative to its' wavelength. A diffuse reflection is a bumpy surface relative to its' wavelength. Most objects are diffuse, and because of it's not smooth surface, it allows us to see the image. As I said in the last blog post, a mirror is opaque, and gives off a specular reflection of light. In this picture, I can see my full body in the mirror, because the mirror is greater then half the length of my body. My feet to my head reflect in the mirror, which reflects back to my eye, which is how I see my whole body. If I were skipping towards myself in the mirror at 3 m/s, the image of me in the mirror and my real body would approach each other at 6 m/s. Because I am using a flat mirror, there is no center of curvature so light isn't conveyed. Because the light isn't conveyed, I can see my reflection very clearly and well.

what you see - unit 10

Today we learned that when you are looking at an object, you aren't actually seeing the object. Instead, light is reflected off of the object, which is what you see. Electromagnetic waves (EM), or electromagnetic radiation, is radiation consisting of self-sustaining oscillating electric and magnetic fields at 90˚ angles facing each other and at the direction of the motion of the em wave is transmitted through a medium such as air or water. It does not require a supporting medium and travels through empty space at the speed of light.

We also learned that objects are either transparent or opaque. If they are transparent, the em frequency is allowed to go through it. If opaque, the em frequency is NOT allowed to go through. The little trinket I bought in china town many years ago on a field trip, is an example of a transparent object. I know that it is transparent because light can go through it, and I can see from one side to another if I look through the glass. Some objects that are not transparent, are mirrors, books, carpet etc.

unit 9

 

Continuing with the topic of waves, today we learned about sound waves. A few key ideas we learned, were that object want to vibrate, and that noise is a sound that is incoherent. Also, sounds need a medium to travel through.
Using a tuning fork, we did multiple labs showing us how sound travels. The average human can hear about 20 Hz - 20,000 Hz. Animals who can hear higher frequencies are called ultrasonic, whereas the opposite, hearing lower frequencies are called infrasonic. 

In this picture that was taken 5-6 years ago, I am with the cutest water mammal, the dolphin! Out of curiosity, I looked up the range of frequencies they can hear. I found that it was a much bigger range (to no surprise), 250 - 150,000 Hz!

Using the beautiful creature, I created a sample problem that shows how to find the frequency, given the speed and wavelength.
If a wave has a wavelength of 2.17 meters and the speed of sound in water is 923,580 m/s, what is the frequency a dolphin hears in this water?

V= ƒλ
92,580 m/s = f (2.17m)
f = 42,664 Hz, 42.7 kHz

Motion of the Ocean - Unit 9

Today we were introduced to waves and wavelengths. From chemistry, I was somewhat familiar with what waves were, and how they contributed to our world. However, there were a lot more aspects and details that we didn't learn, that make "waves" a topic a little more difficult to understand.

I found that when Mr. Blake talked about the ocean's waves in terms of the physics waves, I understood the whole concept a lot better. Below, I will define words that are affiliated with waves, but in terms of the ocean water.

Frequency: The number of waves it takes per one second.
Hertz: Units of frequency (if 3 small waves came in one second that would be 3 Hz. # of cycles/secs)
Amplitude: The height of a wave measuring from sea level.
Wave speed: How fast the wave comes
Wavelength: How long the wave is.



Interference is when two waves meet in the ocean. There are two types of interference: Constructive and destructive. Constructive is when two waves coming from opposite directions meet and create a very large wave, whereas destructive is when two waves coming from above and below meet, creating a completely flat sea level when the leave.

The girl in the picture below is cruising in the water with her doughnut floaty. If 2 waves pass her in three seconds, the speed of the wave can be measured as followed:

V= ƒλ
V = 3/2 Hz(2.5 m)
V=1.5(2.5)
V= 3.75 m/s

What is it's period, or the time it takes for one complete cycle to occur?
T=1/f
T = 1/1.5
T = 2/3, 0.67 sec

Bottle Rocket analysis - quarter 3

What design features worked?
           The size of the fins and how we wrapped duct tape around them seemed to work fine. A few time the rocket landed on a fin and it came off, because the fins were only attached to the bottle by hot glue, but after we duct taped the glued fins to the bottle the fins never came off. The bottle itself never broke apart. Our first nose cone was very good because of the thick paper we used. However, it got stuck in the tree and we were unable to retreive it. We didn't have any more of that paper so we had to use a thinner construction paper. We wrapped the cone in the duct tape too, but it was still flismy, and crushed easily. The only design that didn't work was the parachute. For some reason, we couldn't get it to come out of the cone. Although we tried folding it and placing it inside the cone various different ways, it was never effective.

Launch condition - amount of H2o PSI?
         When we launched it twice in the morning (8ish), there was no wind. We used a lot of water (about 1 L) and realized that it had too much water and it was weighing it down, which constrained it from reaching a higher height. We then tried a little less water (about 3 party cups full of water) and it worked a lot better. We tried to get as much PSI or pound/square inch as we could. We ended up with about 100 or 120 PSI, the highest PSI we could get.

What this taught you about physics and otherwise.
           I learned that there are always variable you don't know about, or don't realize that exist. It's very hard to manipulate your experiment when you are outside. I also learned that expirements are very hard to reproduce, and very hard to predict the outcome - the outcome is different every time!
           Otherwise, I learned that maybe there is such thing as fate, and whatever that's meant to be will happen! I also realized how frustrating it is when something doesn't go the way you planned it and you know why but can't make it change (like with the parachute). Lastly, NEVER GIVE UP! You never know what might happen!

Our highest time in the air: 9.1 sec. Overall, I am very proud of our rocket. We got the second highest time in the class.

carlos - quarter 3

Today we added gazmos and gidgets to our bottles in attempt to making it soar in the the air for at least five seconds. We were allowed to add a nose cone, parachute and fins. With very few limitations (the liquid has to be water, cone must be attatched to bottle etc.) me and my partner blake designed a bottle rocket.

 

Materials used: 

Two 2 L bottles

Lots of duct tape

String
Hot glue gun
Scissors/exacto knife
Clay

Not identical, similar for the most part though.

Plastic bag
Poster board

To elongate our rocket for stability, we used the middle to end section of one water bottle and sealed it to the bottom of the other bottle. We cut out triangular shapes for our fins following an outline found from the internet. We then taped the fins completely with duct tape, to make the fins more firm. We hot glue gunned the fins to the bottom of our rocket, careful to not melt the plastic of the bottle by filling it with water. Our cone was made out of poster board (paper material but much thicker than construction paper) and we just rolled it up so it looked like a party hat. We put a ball of clay along with a dime and balled up tape in the top of the cone, to add mass. Lastly, the hard part: the parachute. Although we tried to follow instructions found online on how to make a parachute, we ended up folding the plastic bag in half, and cutting out a half moon that was hand drawn. It seemed a little small, but we decided on testing it out first. We put eight or so pieces of tape going around the plastic bag, and then hole punched that section so we could string the parachute to the cone. We added tape so the string wouldn't rip through the plastic bag and would be more durable. We did the same thing with the tape and hole punching on the cone. The strings from the parachute and were taped down to the bottle.

When we tested our rocket out, we were dumbfounded that it stayed in the air for so long (about 8 seconds but we didn't time it.) And this was without our parachute deploying. We are very content with our product, but we still have some work to do :(

We named our baby rocket Carlos in case you were wondering!

weeerk - unit 8

Until now, we have been learning about work, or any change in energy. Today we learned about power, and how that is the result of work divided by time. The units are joules/sec, also known as a watt. During our laboratory, we learned that objects that are more massive take more power to move. This is because the rate at which work is being done is greater than the rate of an object that is less massive. The difference between work and power, is that work is the amount of energy an object uses, and power is the rate of the energy being used.

The cost of electricity is about 20c/ Kwh, the following equation is the cost of one light bulb left on for ten hours straight.

0.21 Kw * 10 hrs * 0.20 c/Kw hr = $0.42

potentiality - Unit 8

To blow off steam from a tough day of physics, I went to go work out at my gym after school. During my speed bag lesson, I noticed that there was a pendulum right before my eyes! The speed bag located on a hook (to allow the bag go back and forth) was actually a pendulum! This unit was about work and to understand it, a pendulum was used to show how work is neither created nor destroyed. Where the pendulum lays when no one has touched it, is the equilibrium point. We can call this 0m, and nowhere on the pendulum no matter how it is pushed can go past the equilibrium point. When the weight of the pendulum is brought up above the ground at a certain point and released, the weight should go back and forth and never go higher than the dropping point. When the weight of the pendulum is suspended in the air, it has potential energy, because there is distance for the force of the ball to come down. Because it isn't at its equilibrium point, it has more than 0 potential energy. When the weight is released, the potential energy decreases as the kinetic energy increases (an inverse relationship). When the pendulum is swinging back and force, the equilibrium point is when it'd be going the fastest because there is no force working against it/for it. If you had the same situation (suspending a pendulum above the ground) but pushed the weight of the pendulum forward, no longer will it return to the same spot. It will go back and forth faster, and end up higher than the dropping point. In this video of me speed bag boxing, I am putting energy into the pendulum to make it go back and forth. Because I hit it with a great amount of energy (and the weight is very light) the bag goes back and forth quickly, and hits either side of the top of the pendulum.

the smell of success should NOT be the smell of eggs! - Unit 7

For this project, I was assigned to my partner Nalei. When we came up with an egg catcher, we agreed that in order for there to be less force on the egg (so it won't break), we had to somehow increase the contact time, and decrease the the impulse.

What we did: We used a plastic container and cushioned the bottom and sides with shredded newspaper. There are about ten sheets of newspaper on the bottom of the container, so there is something between the hard plastic and the shredded newspaper. Towards the middle of the container, there is a cup of cotton balls surrounding the egg. The egg is wrapped in one sheet of newspaper, and is sitting on the cotton balls. On top of the wrapped eggs, there are more cotton balls and newspaper.

What we used:
1 plastic container 23 cm in height, 13 cm in width, 17 cm in length.
20-30 cotton balls
15 sheets of newspaper

Why we did: The four inches of newspaper were supposed to cushion the eggs landing, and create a separation between the egg and the plastic. The cotton was supposed to increase the contact time, as well as create more of a cushion. Wrapping the egg in newspaper was supposed to protect the egg more.
...success?

No, I failed. A lot of the mass came from the lid of the plastic container, which we weren't expecting to land on the bottom. The lid split open, and the egg couldn't handle all of the force.

delta P - Unit 7

In this unit, we learned about momentum. In order to find momentum, you must know the mass and velocity. To find the change in momentum, you will have to know the average force and change in time. To be put simply, momentum is just inertia in motion. When we look at momentum between two objects, some things never change. If the two colliding objects have different masses, they will still have the same force of impact, the impulses would be the same, the changes in momentum would be the same (same thing as impulse, changes in momentum and impulse are two interchangeable words), however, the speeds of the two objects will be different (because mass is inversely related to velocity).

Here is a sample problem: A 50kg man is running with a velocity of 10m/s north onto a 1000 kg car. When the man is in the car, the velocity is 15 m/s north. What was the velocity of the car after the man jumped on it?

Equation: MboyiVboyi + McariVcari = (Mboy + Mcar) Vf

50kg(10m/s) + 1000kg(15m/s) = (50kg+1000kg) Vf

500 + 15000 = 1050Vf

15500 = 1050vf

Vf = 14.76 m/s

all work, no play - Unit 7

After our long three day weekend, we got right back into physics by learning the kinematics of collisions. In this picture that mysteriously looks very similar to the one Mr. Blake took, our class is having a water balloon contest. This is to prove that objects have a limit to how much force they can stand. Like someone falling off of a 20 story building, "It's not the fall that kills them, it's the landing surface." What this quote is saying, is that when you are falling, your body increases velocity and the final force you land with is so great that your body can't handle it; therefore you die. Well in this fun activity we did at the end of class, we had to catch the water balloon in such a way that would cushion the water balloon so it wouldn't burst. We learned that if we increase the time where the balloon was caught, the less force would impact the egg. In the equation: delta P/change in time = avg. force, we see that force and time are inversely related, indicating that the more time it takes to catch, the less force will be exerted on that object.

I learned many concepts in this class that I wouldn't have learned in any other class. Most of everything I learned is on other blog posts.
Physics is enjoyable for me because I am finally learning the "behind the scenes" of what's going on when objects are in motion. Many questions I had about why something happens have been answered by taking this class. For example, I always wondered why a ball would still bounce up and down in your hand when you were in a car. Why wouldn't it go flying straight through the back window? I am glad I took this class over the summer. I am also really glad I have friends who I can enjoy this difficult class with. I can rely on them for help, and they make it fun. Four to six hours everyday seem like nothing!
In physics, the concepts were really hard for me to understand the first time around. Since this class is so compressed, we had to learn everything really quickly. The ideas and concepts kept getting harder and harder. This is an ongoing challenge for me, but I've fixed the problem by asking Mr. Blake and Colin for help, asking my wunnerful table mates and going to extra help after school. Because I don't understand everything as well, I need to spend more time on homework.