Physics Class Review

Physics is all around us. I was surprised when I first started noticing concepts I learned in physics class pop up in every day life. It is the science that describes how our world works. I think physics is what moves us forward. It constantly helps us discover new idea and concepts that helps improve our way of life. So, I guess I would define physics as the study of how the world/universe behaves.

In all honesty, I really enjoyed the class. Sometimes, I even felt excited before class started to learn the new concepts. The class moved at a fast, but still comfortable pace for me. I always ended the day feeling like I had learned a lot but never really felt too overwhelmed. before I started the class, I wasn't looking forward to 4 or 7 hours a day in class 5 days a week, but after finishing the class, it feels like it passed by really fast. The classes were very hands-on and interesting, rather than listening to a teacher lecture and give out worksheets.

Now that I look back, I have learned A LOT of information that I had never even dreamed of knowing before this class. We began in Unit 1 which was basically an introduction to physics. Our major focus in Unit 1 was to learn how to analyze and collect data from labs and experiments. We learned a lot about graphing and graph relationships, as well as scientific notation and SI units. Unit 2 is the start of kinematics. Kinematics is the study of motion. We focused on different types of quantities, scalar and vector, like distance, displacement, speed and velocity. We also learned the three main graphing rules for d/t graphs and v/t graphs and how to analyze them. This lesson taught us a lot about interpreting motion through words. Then, in Unit 3 we began uniform acceleration. This lesson is basically like what the title describes it to be. Acceleration is change in velocity/unit of time or m/s over s or m/s^2. Then we learned the relationship between d/t graphs, v/t graphs and a/t graphs. Acceleration is a curved distance vs. time graph and a sloped velocity vs. time graph. We also learned the three kinematic equations, DAT, VAT and VAD (d=at^2+vot, v=vo+at, and v^2=vo^2+2ad). Another important thing we learned is how to organize solving problems; we used the order of d, a, t, v, vo for the givens. Next, in Unit 4 we began projectile motion. One important idea to remember is that axes are independent. We learned that when vertical and horizontal movement is combined, it creates a parabolic motion. This is the unit with lots of word problems. We used trigonometry, like sine, cosine and tangent, to solve some of the problems. Unit 5, we did forces in equilibrium. In this unit we learned a lot about forces and how they act upon each other and other objects. Most importantly we learned the bureku technique, taught by Mr. Blake himself! We also used trigonometry in this unit to solve the diagonal problems we encountered. The bureku technique taught us to break up any diagonal into x and y vectors, and then use trigonometry on the right triangle you just created. We also learned Newton's three laws. The first law is the law of inertia, the second is the law of acceleration and the third law, is the action-reaction law. We also learned that one Newton (N) = kg*m/s^2 and weight = mg. An important thing to remember is that a normal force is the force perpendicular to the surface. This unit focused a lot on balanced and unbalanced forces. In Unit 6, we focused on friction. There are two main types of friction, static friction and kinetic friction. Force of friction is represented like this Ff which is equal to the M*N. Next, in Unit 7, we learned about momentum. Momentum (p) is mass (m) x velocity (v). The units for momentum is kg x m/s. The law of Conservation of Momentum is: In a closed system, momentum of a system is always conserved. Force = change in p/ change in t. The change in p is the force x time or the Impulse. Also, the pfinal - pintial = F x change in time. We learned concepts on how momentum is always conserved and elastic and inelastic collisions. Then, in Unit 8 we learned all about work and energy. The Law of conservation of mass is: Energy cannot be created or destroyed, it can only change forms. With this in mind, we learned different types of energy, kinetic and potential, and how to find the work. There is also spring potential energy which deals with energy of springs. We also learned some graphing rules with force vs. distance graphs. power is the rate at which work is done. The units for power is joules/sec or watts. In Unit 9, we work on waves, YAY! We determine the difference between transverse and longitudinal waves, we see how medium affects waves, and find the relationship between velocity and frequency and wavelength. We learn superposition and how waves interfere, as well as resonance and pitch. Unit 10 we learn the speed of light, which is 3x10^8 and the difference between sound an light waves. We learned opaque and transparent, and the whole spectrum of electromagnetic waves, from low frequency things like radios, to high frequency light like ultraviolet, and x-rays and gamma rays. Specular is a smooth surface and diffuse is a bumpy surface. White light is a light with all frequencies of light, ROYGBIV. We learned how to mix light colors and that objects reflect certain colors and absorb others.

I really liked this class because Mr. Blake made it a very hands-on and interactive class. I am a very visual and hands-on person, so when I get to experience the concepts of physics first hand, I really understand the concepts better and it is WAY more enjoyable for me. I liked the review sessions we had because it touched up on very important things and allowed me to ask questions that I never thought of before. It was great that they were right before the test. I also liked that Mr. Blake gave us progress reports because it let me know how I was doing in the class. I know I said that visual learning and hands-on experiences were important to me, but so was the packet. The packet was very useful for practice problems and when I needed to look back for a quick review or look back what we did. I sincerely enjoyed the class a lot more than I thought. I took this class to find out if I would be interested in these types of sciences, and I certainly am! I look forward to maybe pursuing more of this interest.

Something the class could improve on was having more field trips to places outside of Punahou. Also, I think it would be fun if we had more projects to do instead of tests, wink wink.

Thank you Mr. Blake for being so helpful. You really did make learning fun and interesting with your jokes. Your interactiveness and fun personality made it easy for me to ask questions and really get into physics, thanks! Kamehameha is really lucky to have you.

Unit 10: Light Properties (refraction)

Today was all about refraction. Refraction id the bending in waves due to change in media. For example, when light shines through a pool, the light doesn't shine in a straight beam, it looks like its bent. This is refraction because it bends form the change in the material the light is in. One major rule for refraction is that when moving from a fast medium to a slower medium, light will bend toward the normal. The normal is the force perpendicular to the surface.

In the picture above, the laser is moving through a fast medium at first, then the medium changes to a slower medium, causing the laser to bend. Then the laser moves back into a the faster medium again and is going at the same velocity and angle as it was before. As you can see, the laser wanted to continue going in the same direction after hitting the different medium, represented by the dotted green line, but the laser bends in the slower medium toward the normal (N) force, which is represented by the dashed blue line.

Different colors bend at different rates. Red bends less and blue bends more.

Another important rule to remember is Snell's Law which is: n1sinθ1 = n2sinθ2. "n" is the index of refraction, which is a ratio, so there are no fractions. n = c/v. "c" is the speed of light in a vacuum, and "v" is the speed of light in the medium. Here are some common ones:

nvacuum = 1

nair ≈ 1

nH2O = 1.33

nglass = 1.5

ndiamond = 2.42

All angles are relative to the normal. When the light is moving from a fast medium to slow medium, the light bends toward the normal, whereas when the light moves from a slow medium to a fast medium then the light bends away from the normal.

We also learned about lenses. Lenses can be either concave or convex. When light goes through either of them, the image created can either be real or virtual, inverted or right-side up, and reduced or enlarged.

In the picture above, I am holding up paper and a magnifying glass because in class we used convex lenses to create a focal point with the sun's light and burn paper. That is why the paper I am holding up has holes in it.

hehehe.

Unit 10: Light properties (reflection)

Today we learned a lot about reflection. The two main types of reflection are specular reflection and diffuse reflection. Specular is when the surface is relatively smooth compared to the wavelength of the wave. Diffuse is when the surface of the object is bumpy/rough when compare to the wavelength of the wave. This means when light reflects off of a specular object, the light reflects off of a mirror-like object in a single direction and when light reflects off of a diffuse object, the light reflects in all different directions. This is because of the law of reflection. The law of reflection states that the angle of incidence is equal to the angle of of reflection, relative to the normal. The normal is a force perpendicular to the surface, so when the surface is smooth, there is on normal, but when the surface is bumpy there are many different normals, and therefore many different directions the light is reflected.

Today we also did a lot of work on color and color mixing. This is not the same type of color mixing you do in art class, because that is with pigments. This type of color mixing is using light. here is the basic color chart to follow.

Complimentary colors (colors on oppos. sides) create white.

White light is light with all of the frequencies or, in other words, ROYGBIV. Objects reflect certain colros and absorb certain colors. For example, a blue shirt that you own is blue because the shirt was made to absorb all of the other colors and reflect blue. When there is a shadow, there is an absence of light because all of the colors are absorbed and therefore it is black. That is why, when you wear a white shirt, you reflect all of the colors, but when you wear black, you feel hotter because it absorbs all of the colors.

 Here are two pictures (above and below) of when we used blue, red and green projectors in class to mix the lights and make shadows. The picture above is of Mr. Blake and the picture below is of me.

The picture below is when we used lasers to experience how light reflects. You can only see the beams if the air is junk, so we sprayed stuff in the air so that we could see the laser beams. cool.

Extra Credit - Parents Show and Tell

Me and my dad :)

Unit 10: Light and Color

Today we learned about light and color.In the last unit we learned that sound is a pressure wave, but in this unit we learn about light and that it is a electromagnetic wave. The electromagnetic spectrum is a range of all electro magnetic waves. Electro magnetic waves are transversal waves that are perpendicular to each other. Some things we have to know before I talk about the range, are vocabulary. Opaque means light cannot pass through and transparent is when waves can go through.

The lowest frequencies in the spectrum are radios, TVs and cellphone. Theses range anywhere from 500 KHz to 1000 KHz. Next level is microwaves. The frequency of microwaves is the resonance of water. The next level is infrared. Infrared literally means "below red". Infrared light is heat energy and radiation. This is used to sometimes detect people through walls for police. Then comes the visible spectrum, which means the RAINBOW! This includes ROYGBIV. The only light visible to humans is between 4x10^14 to 7x10^14 Hz. Red starting as the lowest frequency and longer wavelengths to violet, which is higher frequency with shorter wavelengths. red has the lower energy while violet has higher energy. After visible frequencies is the ultraviolet (above violet). This is also known as UV and has different types like UVA and UVB and this is given off by the sun. Ultraviolet is opaque to the ozone layer and glass. And finally, the highest frequencies are X- rays and gamma - rays. These can go through just about everything except bones.

As you can see in the picture above, I use Neutrogena sunblock with SPF 55 when I go out and play tennis. I use it mostly because it smells better than other sunblocks and isn't oily but that is besides the point. The main purpose for this is to protect my skin. Luckily for me I have a higher melanin in my skin because I don't burn as much, I just get really tan. Like it says on the bottle, it has UVA and UVB protection. The main use for sunblock is to literally block the sun. It makes your skin more opaque to ultraviolet light. COOL.

Unit 9: Sound and Waves continued

In continuation of unit 9 we learned more about sounds and waves. Sound is the longitudinal wave from vibrations. We learned the range of sound for humans. Humans range of hearing usually is around 20Hz to 20,000Hz. Ultrasonic sounds, sounds that are over 20,000Hz are very high pitched and are what bats and dogs hear. In fact, bats use ultrasonic sounds to communicate. Infrasonic sounds are sounds that are below 20 Hz and are used by elephants to communicate. These types of sounds are so low pitched that we can't hear it. That is why animals can sense things happening, like natural disasters, before they actually happen. So, if I ever see my dog going nuts, I will run for my life (I'm just being dramatic).

We also learned that refraction is the bending of waves due to the change in medium and reflection is the bouncing of waves. Resonance is the building up of energy and dispersion is the spreading of waves. we also learned that sound travels fastest in solids, next fastest in liquids and slowest in gases.

In class, we did a lab using tuning forks. We filled a graduated cylinder with water and had a tube inside. We then jolted the tuning fork so that it would begin to vibrate. Then we held the fork over the tube while moving the tube up and down to find the perfect length of 1/4 of a wave. Each tuning fork has a specific note that it makes when vibrating. After finding the 1/4 of a wave we multiplied it by four to find the length of one whole wave.

In the picture above, I am making music with the wine glass with water in it. I am making the glass vibrate so that it creates a sound with different pitches depending on how full the glass is of water. Pich is the frequency of sound Unfortunately, I just lied to you because the wine glass in the picture is made out of crystal and doesn't have the same effect.

Unit 9: Waves and Sound

Today we learned all about waves and sound for unit 9. We learned that a wiggle in time is vibration and a wiggle in time and space is a wave. So when you are "waving" to some one, you cannot be standing still because that wouldn't be waving, it would be vibrating. Here is a diagram of what we learned about waves:

One whole waves length includes the up loop and the down loop. It is measured from two identical places in the wave. The crest is the top of a wave and the tough is the bottom of a wave. The dotted line is where the wave is at equilibrium. A wave is just an energy flowing through a medium. A medium is the material the wave is in. Wave length can be represented by a lambda symbol.

Amplitude is the distance from equilibrium point to highest/lowest point in the wave. Period (T) is the time is takes for one whole cycle to occur and frequency (f) is how many cycles pass in a second. the unit for frequency is Hertz (Hz) or 1/sec. An equation for this is T= 1/f. Also to fin the velocity of a wave, you use the equation v = wavelength x frequency. Wavelength and frequency are inversely related. Only tension and medium affect the velocity, but the wavelength and period are directly related.

A transeverse wave is wave energy that moves perpendicular to wave velocity. A longitudinal wave is wave energy that moves parallel to wave velocity.

In this picture I am blowing a whistle. This is a rape whistle so it makes a very loud and high pitched noise. It is very high pitched because it has a really high frequency.