Last But Not Least

Writing this last blogpost is somewhat bittersweet... or just sweet. I'm not gonna lie, I won't miss writing these every night. As interesting as physics turned out to be, I'm really looking forward to waking up at noon and not retaining any information whatsoever.

Physics is an explanation. It's why the sky is blue, and why rainbows exist. It's how we stay on planet Earth and don't float off into space. It's how we can send rockets into the atmosphere, and why waving goodbye isn't really a wave. That's what I've decided, anyway. And according to Moodle, it's also the branch of science dealing with the study of matter and energy, used to explore motion, forces, momentum, energy, waves, and optics.

The class turned out to be pretty fun. I'm definitely happy I chose to take this over the summer, since I think that my understanding of physics benefited from being the only subject I had to focus on. As exhausting as 4-6 hour class can be, for the most part the hours went by quickly, since we always had a lot to do to keep our minds occupied.

I learned a lot of things which will probably be of no use to me other than being interesting facts to spout off when needed. At the very least, it's stuff I find interesting, so not a total waste of a summer. These last few days of class have been the most interesting to me, like finding out how we see color, or how glasses keep me from being blind. I've also learned that I don't hate math as much as I thought I did. When used like this, where we can just put numbers into an equation without doing too much thinking, I even find math tolerable.

One thing that I think would make the class even better would be having more breaks. I'm not just saying this to get out of class time, I just honestly feel like it's easier to pay attention with a couple more breaks. They don't need to be particularly long, but maybe an extra five minute break to go get food or just not have to take in more information would be greatly appreciated. But overall, I genuinely enjoyed taking physics this summer, so thanks for a great summer Mr. Blake!

Light Refraction

Moving from reflection to refraction today, we learned about the bending of light instead of the bouncing of light. Light refraction happens in lenses, or even in raindrops. It's how we can see rainbows, and how we can set physics notes on fire in the quad with magnifying glasses. Another application of refracting light happens in our eyes. As someone who's worn glasses or contacts since the 2nd grade, I actually found this pretty interesting. When light hits someones eye, the light bends at the lens of our eye, refracting it so that it hits the retina, so that we can see the light. For me, because I'm nearsighted, the lens of my eye doesn't quite bend the light the right way, so the light actually hits just before my retina, making everything blurry. My glasses bend the light in such a way that it hits exactly my retina, letting me see clearly.

Light Mixing

           Mr. Blake warned us that today was his favorite day, but (no offense, Mr. Blake) I wasn't too excited because I couldn't be sure that he wasn't super stoked about some new equation or other mathematic hell.  As it turned out though, the day was really cool. We learned about how colored lights work, and the day ended up looking something like this:

            We relearned the color wheel from first grade art class, but now instead of using it for pigments, we're using it as the color that gets reflected from a surface. For example, the reason my wall is blue (besides an extraordinary amount of paint) is that when a white light is shone on it, there are red, orange, yellow, green, blue, indigo, and violet rays all hitting the wall. Because the wall is blue, it's only going to reflect the blue light into our eyes, so that we see it as blue. All the other colors will be absorbed by the wall, so that all we see is the blue.

Unit 10 - Light and Color

Today we began our last unit, about light and color. Light is a wave, like the waves that we learned about last unit, except these are electromagnetic waves. There's an electromagnetic spectrum, which holds the range of different wavelengths, frequencies, and energies. This range goes from violet to red, and from a higher frequency to a lower frequency. The higher the frequency is, the more energy it has.

Different electronic devices have different types and frequencies of waves. For example, radios and TV's have a range of about 500 kilohertz to 1000 megahertz. Basically, all you need to hear a certain channel or station is a device that can get to the right frequency. You can even listen in on phone calls by figuring out a certain phones frequency and matching it.

Unit 9 - Waves and Sound

 Sound is a vibration that causes a longitudinal wave
Pitch is the frequency of sound, the higher the frequency, the higher the pitch, and vice versa. All frequencies travel at the same speed if it's at the same temperature.

One thing that I learned about waves and sound that's actually really applicable to my life would be about the waves in garage/gate openers. I know the exact spot that I can click my gate opener and have it work, and I know that if I'm just a little bit off of that spot then I'm too far away, and the waves won't reach my gate and open it. Mr. Blake told us that if you put your clicker on your elbow or by your head, then the frequency travels through you, basically using you as a human antenna so that the waves can travel further.

Here's how far away from my gate I can be normally, without holding the opener up to my elbow:

And here's how far away I can be when I do hold the opener up to my elbow:

Unit 9 - Waves

      

 

     This picture doesn't actually show a wave very well... but let's just pretend. The 'wave' in the picture, appears to be moving towards the shore. This isn't technically true, since it's only the wave energy that's moving, while the water is just the medium that the energy is moving through. It's a transverse wave, because the energy is moving perpendicular to the velocity of the wave. Throughout the duration of this wave, the velocity should stay constant, even if the amplitude or wavelength changes.

    The principle of superposition states that two different waves can occupy the same space and time. This means that when two waves collide, they actually go through each other instead of bouncing back, the way the carts did when we did the air track labs.

Launch Day

What design features were included in your rocket design?
    Our rocket had fins and a parachute with a funnel functioning as a nose cone. The fins were triangular and on the small side, and the parachute was cut from a white trash bag. Instead of using the whole bag intact, we chose to cut it into a circle so it would have greater air resistance and surface area.We put some clay in the nose cone in hopes that it would help the nose cone come off during the rockets descent.

What worked as planned? What did not work as planned?
    During our best launch time, at 16.7 seconds, our parachute finally deployed. It only deployed towards the end of the rockets descent, but it was still more successful than any of our other launches, when the nose cone wouldn’t come off, keeping the parachute from opening up. The fins seemed to be successful though, as our rocket was pretty much stable throughout all the launches. We had been using a small funnel as a nose cone for the past few days, and for about half of our launches today. During one of the rockets launches, the funnel broke upon impact. Luckily we had an extra funnel, that was slightly bigger. It seemed to make it easier for the nose cone to come off and let the parachute expand, giving us more time in the air.

psi at launch - 80
Amount of water in bottle - about half full, slightly under.

The physics learned - We learned (mostly by trial and error) a lot about how much air resistance can affect the rocket. In our case, it worked to our advantage because it was the air resistance that worked with the parachute to keep our rocket in the air for as long as possible. We also learned about how each element of the rocket relates to what kind of flight path it takes. The higher the psi, the more acceleration the rocket had in the air. On some of the rockets that went REALLY high, you could easily see the “fast slow stop slow fast” idea in action. Pretty much all the rockets went high enough that you could see it’s jump in acceleration as it got closer to the ground. I’m super proud of our class since our average was well above 8 at 10.9!

Rocket Science

Doing actual (water bottle) rocket science was pretty exciting. Not only did Candace, Matt and I get the record for longest launch at 11.87 seconds, we're also feeling confident about our times for tomorrow. Our average launch time was about 8 seconds, and we've gotten our launch system all figured out. After our first launch, the parachute didn't deploy at all. The nose cone didn't even come off the rocket. We had used some clay in the nose cone as extra mass, so for the second launch we took out some of the clay to see if it would make a different. Second launch time had about a second of improvement from the first one, but the parachute still didn't deploy until we were just above the ground. To see if we could make our third launch time any better we increased the length of our strings attached to the parachute. With that adjustment, we made it to 11.87 seconds and the parachute deployed. We were originally planning on using this rocket as a test rocket, and recreating it with all the best aspects again tomorrow morning, but now we're afraid to jinx our luck so we'll keep the rocket for the launches tomorrow as well.

Power

We discussed the relationships between force, work, and power today in an activity that involved finding the power of people running up the stairs. In order to find the power of a person, you need to know the work done and time. To calculate the work done, you need the force and the distance. To find the force, you need mass and gravity. It's a long, annoying chain of work that gets simpler with repetition, thankfully. So Power = work / time interval, work = force x distance, and force = mass x gravity.

So let's say my sister is 55 kg, walking up stairs on planet earth, with a distance of 3 meters in 10 seconds. That would make her force 539 N, and her work done 1,617 J, and her power  161.7 W.

Energy & Work

Energy and work, two words I already dislike, now with math.

The law of conservation of energy states that energy cannot be created nor destroyed, it just changes forms. Energy is also a scalar quantity, with no direction, just magnitude. There are several different kinds of energy, including kinetic and potential. Kinetic energy is the energy of motion, and it is calculated by half the mass multiplied by the square of the velocity of the object. Potential energy is the energy that an object has the potential of achieving. It's calculated  by the mass multiplied by gravity and change in height.

Work is a change in energy. It's calculated by force multiplied by distance, and it's units are joules, or Newtons multiplied by meters.

In this photo, with my dad enthusiastically running on the elliptical, he's showing work, or a change in kinetic energy because he started at a lower speed and gradually increased.

We also discussed Hooke's law, which states that the force of a spring is equal to -kd, with - indicating direction, k indicating the spring constant, or the slope, and d meaning distance that the spring is stretched or compressed.

Egg Drop

Pre-drop:
Candace and I worked together to make a device to hold our egg to (hopefully) make it survive the 3 story fall. We have a small mailing box from the post office packed with bubble wrap and a towel for the egg. It's dimensions were 17 x 18.5 x 18.5 cm. The mailing box has a good amount of surface area on the bottom, which I hope will cause more air resistance. All the bubble wrap surrounded the egg will ideally keep the egg from bouncing around in the box, and will keep it stable and in place throughout the fall. We decided against wrapping the box in bubble wrap, because we didn't want the bubble wrap to cause our device to bounce around, which as we have learned causes more force.

Our box, pre-drop:

The forces acting on our box during the fall were gravity (or mass x acceleration) and air resistance. The weight of the box is what was pulling it down, and the air resistance was what kept it from falling faster.

The distance:

Our box, post-drop:

As our box was falling, I was actually feeling pretty confident. But as it hit the ground, it hit on the edge and flipped over a couple of times. At the time, it was terrifying and I thought the extra motion would cause the egg to crack. But back in class, Mr. Blake explained that it landing on the corner was actually ideal, because it had a better chance of compressing without damaging the egg and increasing contact time. So when I cut our box open and dug through the bubble wrap, our egg was alive! no cracks, smile intact. Looking back, I think a change that I would have made to our box would be using a bigger, flatter box, instead of a relatively square one in order to increase air resistance.

We named her Sunny.

Unit 7

One of the hardest parts about this lesson is how there are so many values that are the same, but have different names. For example, impulse = jimpulse = change in momentum = average force multiplied by change in time = mass multiplied by final velocity - mass multiplied by initial velocity.

One of our demonstrations today was about momentum and impulse, and we had one person on the hovercraft and one person on the danger board, and we observed how they accelerated in different directions after throwing or catching the medicine ball. When the medicine was thrown, the mass of the system was changing, same as when the ball was caught. The change in mass is what caused the hovercraft and danger board to accelerate. Momentum is mass multiplied by velocity, so when the mass changed so does the momentum.

Momentum

When I think of momentum, what first comes to mind is someone running full speed toward a fixed point. In class today we learned that momentum is mass multiplied by velocity, it's a vector quantity, and its units are kg x m/s

Momentum (p) = mass (m) x velocity (v)

Impulse is the average force upon the object multiplied by the time the force is acting upon the object. It's also the change in momentum.

Force = change in momentum/change in time

change in momentum = force x change in time = impulse

In the lab we did today we used the air tracks again (for the last time!) to calculate how mass and velocity affect the momentum of objects. We did 9 different scenarios, with different masses and directions and velocities in each in order to see their affect on the momentum. We used the data and the equation for momentum to see that momentum is conserved.