DOOOONE :(

Physics is all kinds of things! From pendulums to the speed of light, we learned so much in this class. If i were to google the proper definition of "Physics" I would come up with "The branch of science concerned with the nature and properties of matter and energy," but to  me, it will always be "The best Summer School class ever." We learned sooo much in such a short span of time. We rolled, dropped, shot, threw, pumped, moved, and broke all kinds of items from eggs to rockets and a bunch of things in between. I admit, I had a ton of fun in this class and 6 weeks of physics definitely flew by! I completely understand all of the concepts we were taught in this class and even those crazy equations! You made it really fun and easy to learn everything without rushing us or stretching a lesson longer than needed. 


Everywhere where I go, all i can think about are Physics. Seriously. When i'm on the bus, and it comes to a stop the whole bus whiplashes back and now i know why. Newton's first law: objects in motion tend to stay in motion! Its crazy. I learned all about velocity and mass, even the difference between that and weight because they definitely aren't the same thing! Even learning about acceleration and collisions was fun! The equations with used, DAT VAT VAD and D=VT will probably stay in my mind forever. We learned about things like gravity, which pulls at a force of 9.8m/s^2, projectiles and the rate at which an object would fall, conversions from kilo to centi, to our recent lessons including waves and the speed of light in certain media. 


I can say I liked everything about this class. Even those darn exams and everynight blog posts weren't so bad after all. I loved how the labs were fun and educational at the same time, also that we had many opportunities to work in other groups, and not only ours but those around us. I like how we used the remotes to answer questions and do some review! It really helped before those tests to go over things that we didn't understand and while using them on the test it was simple to just plug in our answers on the remotes. And I especially liked your music playlist! It made it all the better! Also, the short breaks we got between actually learning were good, and the long lunch break we got was helpful because even if we didn't finish at 2:30, it gave us more time to get our food, come back, and then be immersed in physics. 
I know we learned more than the guys next door! haha the ones in back of the boards that is.. But i think we had more fun than either class! I wouldn't change anything about it. :D

A little something from every unit, sorry it's a very bad picture!

refraction!

Refraction is the change in light speed due to change in medium! Refraction is dependent on the speed of light in the medium it's travelling through. We use the equation n=c/v, c standing for the speed of light in a vacuum which is 3x10^8m/s, v for the speed of light in the medium and n for the index of refraction. We used this equation to find the speed of light in air (n air) which is 1, by dividing 3x10^8m/s by 3x10^8m/s (c/n) and since the meters per second cancels out there is no units for the index of refraction. n and c have an inverse relationship meaning as the index of refraction goes up, the speed of light in a vacuum decreases. 

We can apply Snell's Law to refraction, which is n1Sinϑ1=n2Sinϑ2. To determine the direction of the refracted ray we can use our equation and plug in all the numbers we know in order to solve. The pencil goes from air to water, so air's index of refraction is 1 by using the equation n=c/v and dividing the speed of light by 3.0x10^8m/s, then to find the index of refraction of water you use the same equation but instead plug in 2.25x10^8m/s for v and get 1.33. If the angle the pencil is coming at is 60 degrees from the water, Theta1 would be 30 degrees. The pencil is going from fast to slow so n1<n2 and ϑ1>ϑ2.If i stuck my pencil perpendicular to the surface, there would be no bending since that is the normal. The light is coming from the top of the room, so if i use Snell's Law i can find the angle water bends the pencil at! It would bend more to the center or normal so to the left a little. Here's the work! vv 

We can also use Snell's Law to find the critical angle of object that go from a slow to fast medium such as water to air if the light source is coming from the water. This time n1 would be greater than n2 and we'd set it up as sin-1(1/1.3). 

We also learned about light that goes through different shaped lenses. An object in front of a lens in the shape of a long oval with light will send a ray parallel to the ground, then once it hits the lens, it travels towards the focal point on the images side going down. A parallel ray is parallel to the optic axis, meaning that light that hits there, will stay there. The focal ray will go through the focal point and then bend parallel to the optic axis. Light that hits the focal point on the object's side will travel downwards, then hits the normal coming from the lens and travel parallel to the surface. Another ray that hits the center in the middle of the lens will travel down and they will all meet causing the image to be ral and inverted because it shows up upside down and enlarged. I hope that makes sense! :] 

Reflections!

Today we learned about light and reflection. There are two types of reflection, specular and diffuse. Specular (regular) is when light is reflected off of a smooth surface, while diffuse is when it is reflected off of a rough surface. Some specular items include mirrors and smooth bodies of water. The angle of incidence is equal to the angle of reflection so ϑi=ϑr.All the angles are relative to the normal. Some examples of a diffuse surface are paper, cloth, or asphalt. 

Here's a venn diagram of the three primary colors of white light and their mixtures!

Complimentary colors are two colors that when put together, they make white. So for example the complimentary of blue would be yellow. In class we did a lot with the color projectors so for example, there were the words Red, Green, Blue, and Black written in their matching colors, and when the projector shined specific color light on the board there were different results. The red cancelled out with the projected light, but the green shone when in green light because the light needs to be the same frequency to fully blend in. When we were looking in the light spectrums we compared the light in the classroom to the sun's rays outside. The colors were more blended and stronger than indoors.

We used the equation v=fλ to solve for frequencies, wavelength, and velocities of light using 3x10^8 m/s as the speed of light! To find the distance of a light year, we could use the equation d=vt and plug in the speed of light for velocity and convert our time to seconds then multiply. 


Onto more reflection! While doing our lab with the light thingies, we could see the reflection of light rays when directed by different types of mirrors such as a flat one, a concave one, and a convex one. Concave is when it bends inwards and convex is when it bends outwards. When light rays are reflected from a concave mirror, they create a focal point where all the rays meet. Unlike concave, convex mirrors send the rays outwards where they will never collide with each other. The flat mirror caused the reflection to move in a direction with the same angle as it was bent at. Light bounces off of a source so that our eyes can see them, if it is unable to get to the object, you can't see the light reflected off of it!

Unit 10

LIGHT :D

Electromagnetic Waves are those that have transverse waves travelling perpendicular to the energy travelling longitudinally, (like what we did in class with out hands!) these are given off by light. We learned about light and waves today and how light has to strike an object and reflect it back into our eyes. Thats how we see colors and objects! There are two types of light, transparent and opaque (although it is relative). Transparent is when lights allows electromagnetic waves through, not visible to our sight. Opaque light is when electromagnetic waves aren't allowed to go through, thus making them visible to us. For example: Windows. A light year is the time it takes for light to travel for a year, but is measured as distance. The speed of light is about 3x10^8 m/s, faster than the speed of sound which is why there is a loud boom when you break the sound barrier!

More waves!

Today we used the equations V=fλ which is wave speed equals frequency (in Hertz) times lambda (wavelength). We looked at a stretch of string connected to a wave driver and a pulley.By increasing the frequency, you directly increase the velocity, but frequency and wavelength have an indirect relationship meaning as one goes up, the other goes down. We were also able to count the nodes that were unmoving and the antinodes which were vibrating up and down, but the amount of wavelengths is less than both because it is the distance from one spot to another of the same equilibrium. 

An object's "natural frequency" is the frequency an object wants to vibrate at and resonance is the overall adding of wave energies. Sound is a longitudinal wave that needs a medium (what it travels through), without a medium, it cannot exist! The speed of sound is relatively constant. The equation for this is Vs=331m/s+Tc(0.6). 331m/s stands for the speed of sound at zero degrees celsius and Tc is temperature in celsius. Temperature is average kinetic energy, or energy in motion. The speed of sound in the air at room temperature in Hawaii would be approximately 346m/s. Here's how to do it:
Vs=331m/s+Tc(0.6)
85 degrees Fahrenheit=~24.4 degrees Celsius
Vs=331m/s+24.4(0.6)
So the answer comes out to 331+14.64=345.64 or 346m/s!
We also calculated percent error which is ltest-acceptl / accept. So if our experimented speed of sound product was 328 we can set it up like this
l328-346l / 346 = 0.052 so move it over two decimal places and you get ~5% percent error!

WAVES

We talked all about waves and frequencies and defined a whole lot of words today!
A vibration is the back and forth AND BACK motion or "oscillation" which is a cycle of movement. A wave is basically a transfer of energy. What it moves in is called the medium.

We were working a lot with slinkies today because they're a really good example of different sizes and types of waves! There are two types of waves that we created, transverse and longitudinal. Transverse waves are when the energy is moving in the direction perpendicular , and longitudinal is when they travel parallel (in the same direction). So when we were working with the slinkies, to make a longitudinal wave, you would push the slinky forward and pull it back to create a wave. To make a transverse on, you would move it left or right and return to the same spot, this causes the energy to travel side up and down, while it goes to the side until the end of the slinky. The wavelength is the distance or length of wave from two equal spots, usually from trough-to-trough or crest-to-crest. The amplitude would be the distance from the starting point to either a trough or crest!



As you can see in the photo I'm holding the slinky with both hands and having a pretty even curve. The area that is compressed is the part hat bends. It's compressed because that is where the slinky wires come together, and the areas where it's looser is the long end. This is the rarefaction. By using slinkies we can conclude that the tension of the slinky affects the speed of the wave because a higher tension makes the energy move faster. Also that the amplitude of the wave doesn't affect the speed, along with the wavelength because they still end up being the same! The parts that don't move in a wave are called nodes, and the areas that move are antinodes. We used a lot of this equation: V=F(lambda) I don't know how to do the squiggly line...but Velocity equals frequency times lambda!

Another way of looking at waves is to look at the ocean! I learned today that waves do NOT bounce off of each other (even though it may look that way), but travel through them and continue on their merry way! A period of a wave is the time it takes for one cycle to occur, or for it to return to its original spot. A water wave would be an example of a dispersive wave. This is when a wavelength will affect the speed, compared to a non-dispersive wave which is one that has all waves travel at the same speed in the same medium, not matter what your frequency is (like a sound wave). There are also constructive and destructive waves. Constructive are when two waves come together to create a larger one. A destructive wave is when they are opposite, one positive and one negative, and they cancel each other power out to create a flatline.

Yesterday!

We mainly did review, our exam, and building rockets. For building, Juliet and I created a rocket that was about 1 1/2 feet. This is actually our rocket from today, but to get a picture of what it looked like yesterday, here's a description. One 2L bottle with fins half the size, and a very bright nose cone made of thick paper and pink duct tape! Our absolute first parachute was a 7-11 regular sized plastic bag. We cut the handles to make 4 ends to attach the string to. Our parachute seemed to be the right size compared tot he rest of our bottle. The fins were half the size of those in the picture, but the same design. If you looked at it from the bottle cap area, there would be a pocket in the shape of a V sticking out from the bottle. We assumed the air would catch in here, holding it in the air for a longer period of time. This shot up into the air, but not very high having a total of about 3 seconds. Our problem with this one was that we didn't have enough mass in the nose cone to make it shoot high, and also the parachute wouldn't deploy. This caused it to go off it's path and fall to the ground. By the time we had finished and tested this design it was time to return to class.

BOTTLE ROCKET

We started with a different design than we ended with. Our first design was a single 2-Liter bottle. It had 3 separate fins in 3 equally spaced-apart places. The fins were made of two pieces of cardboard in right triangles put together with duct tape. The tape was all around and then glued in the middle together to ensure it holds. To put them on our bottle we used the hot glue gun on the fin itself then glued around the fins while holding the bottle down. Then when that dried we made the nose cone. The nose cone was made of thick paper similar to that of a manilla folder. I rounded it into a long cone about 5 inches tall and taped it together. We glued an eraser to the middle of it to hold down our mass which was in the center at the tip. Then to create the parachute, at first we used a long rectangle of thin garbage bag. We connected it at the four tips and taped them, then I tied strings about 2 feet long (each) to the ends and we used hot glue and glued the string to four equal sides at the top of the bottle. We taped it down to secure its hold. We then went out and tested this. It had a time of about 3 seconds. Our completed bottle along with the nose cone was about 1 3/4 feet, which was really small. There were a couple of pros and cons with having a small mass. It was good because on the way down, it would float for longer in the air, but was bad because it wouldn't shoot up so far! It would need more mass to carry it through the air higher. 

Since our first one didn't work... we made a new one with a longer design and more mass. Our second rocket was made of an untouched 2L bottle and another half bottle at the end. Glued and taped together it was about 2 feet long. I cut fins which was the same shape as before but bigger. The fins were two pieces of cardboard put together with the same design and attached the same way (glue and more glue). The fins would stay on the bottle sides for a measurement of about 4 inches and then the rest wouldn't attach because the bottle would near it's tip where the cap would stay. I also made tiny fins for the top portion to hold the nose cone in place, which wasn't really necessary I guess. We kept the same nose cone, but added mass to the center of it using coins that were rolled up and wrapped in tape, then glued to the middle. Since we'd punched a hole in the nose cone at the rim, that's where I tied the string on. Then we glued the end of that string onto the bottom of the rocket near where the parachute strings would be. After that we made the parachute. It was a circle this time instead of a rectangle which we hoped would work better and in some ways it did. The string to attach it to the rocket was about 1 1/2 feet. The parachute had pieces of tape cut out equally-spaced apart with holes punched to string he yarn through. After tying string to the parachute we went on to attach it to the rocket. We used the same method as before and glued it down with tape on top, but instead we attached it to the INside of the bottle. When we were finished connecting the parachute, we had some trouble with the string. It tangled really easy, which was on of the problems in our previous design, but this time we had even more string than before. To fix this we just tied a piece of string around the tangle at the bottom near the rocket and left the parachute the way it was, which could fully deploy. We went out and tested our new rocket. The time had increased, but not by much, maybe about a second higher than before. 

One thing that had worked with our new design was that the parachute had deployed! The sad thing was that the nose cone would fly off (well it did twice) and detach itself from the rocket even with the glue and tape securing it. We tested this design about 3 times and the last two times were only over 3 seconds, and over 4 seconds. 

Both designs we filled our rocket about halfway so maybe 1L. The pressure pumped was 80 and less sometimes to maybe 70. I can't be sure since I was pulling the string. I would think that the more pressure there was in the bottle, the more force it has to push OUT of it. And also that the more water we put in, the more water it has to accelerate it upwards because if you had less, all you have would be air pushing out, which wouldn't be as strong as water.

What I've learned about physics is that there are so many sources of error! No matter how hard we try, it is almost impossible to have it shoot at 90 degrees from the ground and have it stay straight in the air. There is air resistance pulling on it when it flies from the fins and the bottle itself. Then there is gravity pulling the rocket down. It hits the ground at the same force that it was shot up at (about).

 some really baaad pictures

Power

We learned about Power today! Power is the rate at which work is done.
So it's work over time, or joules per second. The unit of power is a watt. In class today we were looking at how much power we use to run up stairs and we found out all the variables such as our mass (in kilograms), gravity, force in newtons, height of the stairs and each one, time it takes to run up the stairs, and then found our power by using our equations. So i recreated this at home
If my mass is about 56 kg, and the height of the total stairs is .762m and gravity is 10m/s i could find my work by multiplying force (mass x gravity=56x10) so i get 560 N then multiply it by the height i get 426.72 Joules. Then to find my power I divide work by time and if my time is about .2 seconds and end up with 2133.6 Watts

that's me stepping...


We also went over some older equations with work such as...
Work=Force x distance
PEg=Mass x Gravity x Height
KE=1/2mv^2
PEs (spring)=1/2kd^2

We would plug and chug numbers in to find the speed if we didn't know them, total energy and distance a spring would be compressed.

Yay! :]

UNIT 8!

Last unit of the quarter!
So today we learned about work and different types of energy!
Work is any change in energy so it can also be written as delta E, or W. Work is force times distance and the Sum of energy in is equal to the sum of energy out! The Law of Conservation of Energy is that energy cannot be created nor destroyed, its form can only be changed. So work equals N x M, or units in Joules (J).
We learned about Potential (Gravitational) Energy=PEg=Ug. So delta E=W=F•d=mg•h.
and

Kinetic Energy which is written KE=K=1/2mv^2.
SO there are two examples we used to show where potential and kinetic energy occurs. Firstly the pendulum! I decided to recreate this at home by connecting a broken hand fan (the ones powered by a battery) and taping it to the door frame. I let it go and didn't add any force to it. If the world were a perfect place, it would return to the exact same spot at which it was dropped and go on forever, but no. Since there was frictional forces between the string and the attachment to the door and energy going to friction takes work out, it wouldn't return the same spot. It began with potential energy, but then as it reached the equilibrium point (low pt.) it had kinetic energy, then potential, then returned in the opposite direction with kinetic energy, then ended in potential energy. If it was pushed, I'd be adding energy to it. So it would be potential energy and work together!

The other example we used was dropping an object from a high area. In class we used a bar for example and it was at 100 J, halfway it would be 50J potentional energy, and 50J kinetic energy, then at the bottom of the fall right before landing it would be at 100J kinetic energy. So it would start off with 100J and end up with 100J of energy, proving that Ein=Eout. If for example my shoe had a mass of 2.2kg and fell from a height of 3 m. My energy would be PE=66J, PE=33J/KE=33J, then before it lands it would be at 66J.

THE DROP

I don't know why the second picture is so small, but this is the jar after dropped! So for our design, Sandra and I had a large jar which was under 35 cm tall (the limit) and had stuffed it with padding. The bottom had about 2 full sheets of folded newspaper then onto of that about 5 inches of shredded paper. We then pushed down on it and started layering the shredded paper around the jar creating a small whole in the middle. On top of the shredded paper, we laid cotton balls for cushion. We then left it until we were given the egg. Once we were able to insert it, we surrounded cotton balls and wrapped it in newspaper. We then padded it at the top with about 5 more inches of cotton balls. After we put the lid on and hoped for the best!

A picture of the design

When we weighed our contraption, it was about 410 grams. Ours was dropped first and the result? Disaster! The lid was the heaviest and most massive item, pulling it down top-first. Upon realizing this, it was too late. This was surprising because we had planned for it to fall straight down with the bottom hitting ground first since that was where most of the padding was. Our plan was to increase impact time and decrease force using all the cushion. It was dropped from a height of about 10 m and had a velocity of about 10m/s in the air and a final velocity of 0m/s because of the ground causing it to stop. When it hit the floor, the lid cracked into about 4 pieces and flew around on the ground. It was an inelastic collision because the whole jar had bounced (pretty high!) on impact then fit the ground again. When i retrieved the jar and took out the cotton balls on the top, i noticed the newspaper around the egg was soaked. 

I was surprised at how much force there was on the jar, and since the jar exerts the same amount of force as the ground exerts on the jar it was no wonder our egg cracked. Since the mass of the object was 410 grams, which is converted to 4.1 kg and the velocity was 10 m/s to find the moment we multiply mass (kg) x velocity (m/s) and get 4.1kg•m/s as our momentum. Either way, it was a fun lab to do and watch! :)

Collision and Impulse

We went over more on collision today. When we were looking at the crashed car we noticed that it was an inelastic collision because if it was an elastic one, the two objects would become one but instead they bounced off of each other (in a way). You could see the airbag that had blown up in the car which forced air into a bag and it comes straight at you with a great amount of force in a little time!

We also learned more about impulses and collisions when bouncing water balloons up and down with our towels. I decided to do this at home too! So i filled my water balloon and bounced it up with my little brother. By using the towels we accelerate it up and when it falls down, the towel then absorbs some of the force reducing the force and having it spread out over a longer period of time. Since force and time have an inverse relationship, as one goes up, the other goes down. If we have a long period of time that force is spread out in, the force would be smaller, which doesn't cause the water balloon to break. But if we dropped it on the ground, the stop to the ground applies a lot of force for a very short period of time (less than a second!) Gladly we didn't pop the balloon. :) We plugged in numbers into equations again to find missing variables such as the original velocity, final velocity of an object, or its momentum. We used the equations MaVao+MbVbo=(Ma+Mb)V or MaVao+MbVbo=MaVa+MbVb. We also applied time to find force by using the equation Ft=mv!

Momentum and Such

Today we learned about so many things starting with momentum. This is inertia in motion. Momentum is represented by the letter P with an arrow over it shows that is'a vector with direction. It is measured in the units kg•m/s and equals mass (m) times velocity (v with a vector arrow). P=mv Something very important to remember is that moments is always conserved and also that the Vegas Rule applies here as well. Pin=Pout. So the momentum put into the object is equal to the momentum received.
Total momentum is equal to all momentum added together. Force is equal to the change in momentum (delta p) over the change in time (delta t). Impulse is the average force upon an object multiplied by the time the force is acting on the object. Its equal to the change in momentum!
We also went over how force and time have an inverse relationship! So if the force is low, the time it takes to change momentum is high, but if the time is low, the force exerted on the object is very high!

Another thing we learned with momentum was collisions and the relationship between impulse and momentum, which equal each other. In our lab today we used the air tracks to eliminate friction from our equation. We tested the collision of objects of different weights and speeds and which direction they collided. They all have the same momentum but different velocities. When in collision, the force is transferred from one car to the other causing the carts to move and either increase speed, decrease speed and even come to a stop. The beginning parts we looked at elastic collisions using the rubberbands on the ends of the carts, but when testing inelastic or "sticky" collisions we used clay that stuck the two carts together causing them to travel as one mass and with one velocity. :]

First Semester Flew By!

What did I learn? So much!!
There were so many concepts that I now understand from a few weeks ago which seems so far away! When we started graphing XT, VT, and AT graphs with slope i had some trouble, but now that we've moved onto velocity, kinematics, and acceleration of objects and using all sorts of equations such as D=VT, DAT, VAT, and VAD. We then went onto projectile motion using the x and y axes and finding the best fit for lines on LoggerPro. I felt really comfortable doing these problems because after a while, they became really easy for me! After this we went into Newton's first, second, and third law! We also applied these laws into the more recent problems in unit six involving forces, mass, acceleration, and free body diagrams! I've also learned to DRAW. Drawing out the problem and having a visual aid definitely helps in solving because when you plug in the values to the right areas, it becomes a lot easier to figure out.

I like how we weren't rushed when it came to new lessons. We took things step-by-step and could always ask questions if we had trouble with anything. We had a lot of time to do labs and since Juliet and I are a table of two, it was often we ran into problems, but with time, we were able to understand the concepts and after that they turned into easy questions with simple answers! All of the things we did were hands-on activities where we actually got up and got active! From rolling a ball off a table to launching rockets in lower field, we were always moving around!

I didn't realize that Physics would have so much math in it! I know that we applied some of our Geometry and Trip to Science when we were looking at vectors and the Bureku and Ukerub techniques when solving for SOHCAHTOA. This was one of the challenges for me because math isn't really my strong point :/ but nonetheless i understood how to solve and draw out all our problems! I'm glad i could finally find something useful to apply my math skills to!

(The Physics Syllabus we were given on the first day)

Physics explains why things do what they do! It's eeevvverrryyywwwhhheeerree! :]

Pulleys!

While in class we used those really big machines that were similar to air hockey tables but angled and each had a metal cart that would slide across it. The air between the two metal objects eliminated friction from our equations making it a lot simpler to find the tension. In this lab, we had also had pulleys that change the direction of the force! So by adding and taking away mass from both the cart and pulley's end, we could determine the force and create free body diagrams for this situation. We did a lot of practice problems with the same pulley direction such as those examples from problems we've gone over below.

By using what we've been given, we put the equation Fnet=ma to use! We can use this equation to find the tension of the object pulling. If you think about it, it is the whole setup that is accelerating! Some free body diagrams are shown above.  By multiplying the mass of one of the objects and dividing it by the mass of both objects added together, you can find the acceleration, once you've done that you can use Fnet=ma again and solve for tension by either multiplying the mass of a times the acceleration (which I think is the quickest way) or multiplying the mass of object b and gravity (9.8m/s) minus the tension and equalling the mass of object b times the acceleration. There are three steps to this process, it is first drawing the FBD of the system and there are two since there are two objects relying on the pulley, then find the acceleration of the system, and lastly solving for T using one object at a time. You can check your answer by solving using both equations if you want to. :]

Unit 6

We went over Newton's Third Law of Motion that says for every force, there is an equal and opposite force, having an equal magnitude but going in the opposite direction. This is called Action Reaction. So for example, sitting in a chair. When you sit on a chair, both you and the chair are at rest. Your mass and weight is pushing down while the chair pushes up with the same amount of force. If it is unable to return the same amount of force, the chair breaks! When it breaks, you end up falling and accelerating downwards towards the floor. This can be turned into a free body diagram using the letters N  to represent "Normal" because it can contact with the surface, and mg to represent weight, so there would be two equal vectors. The mg vector will be pointing south and the N vector north, making it balanced. Free body diagrams don't show if an object is moving, but can show if it is accelerating.

If i were to break my chair, my body would accelerate down with constant velocity and keep increasing speed. Ignoring air resistance, my free body diagram would be unbalanced and be just a vector pointing down and have only weight as the south-pointing vector.