Wave Interference Activity: Constructive and Destructive Interference

Constructive Interference

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Constructive interference is when a crest from one source meets a crest from another source, the energies combine to displace the medium (the energies are additive). In other words, when the two crests meet, they produce a single amplitude equal to the sum of the two individual amplitudes. The same thing occurs when trough meets trough. When the crests of the waves line up, there is constructive interference. Often, this is described by saying the waves are “in-phase”. In the first video, we put the slinky on the ground and flicked the same way to represent the crest meeting the other crest. The same thing occurred in the second video except we flicked the other way to represent the trough meeting another trough.

Destructive Interference

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Destructive interference is when a crest and trough meet the energies combine to work against each other- they tend to cancel out. The sum of two waves can be less than either wave and can even be zero. When the crests of the wave in one wave match up with the troughs of the wave in the other, the waves are said to be “out-of-phase”. In this video, the slinky is flicked 2 separate ways to represent a crest and a trough. When they meet, they

Exploring Waves Lab

Pulse Wave

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A pulse wave is a single disturbance that is non-repeating and has one major crest. It often refers to some type of one-time disturbance. A pulse has a velocity and an amplitude but since there is only one crest, there is no frequency or true wavelength, although the width of the pulse relates to its wavelength. To measure a pulse wave’s speed, we use v=d/t.

Periodic Wave

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This type of wave repeats at regular intervals and requires regularly recurring disturbances. Periodic waves are usually characterized by their amplitude, frequency, and wavelength. A wave whose displacement has a periodic variation with time or distance or both.

Transverse Wave

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This type of wave occurs when the spring is pulled sideways. It’s a moving wave that consists of oscillations in which the direction of displacement is perpendicular to the direction of propagation. Transverse waves may occur on a string, on the surface of a liquid, and throughout a solid. Transverse waves cannot propagate in a gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave.

Longitudinal Wave

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A longitudinal wave is one in which the direction of displacement is the same as (parallel) the direction of propagation. It involves a wave consisting of a periodic disturbance or vibration that takes place in the same direction as the advance of the wave.

Archimedes Challenge

History of the Arch Bridge

An arch bridge is a semicircular structure that distributes its weight by dispersing it outwards through arches onto its two abutments, rather than straight down a column or pillar. Arch bridges have been around for about 3,000 years. The oldest arch bridges can be found in Mycenaean Greece but it was the Romans who were to fully realize the potential of arches for bridge construction. An arch bridge built of stone does not require mortar. This may be one of the reasons why arch bridges were invented as there was no mortar until it was invented later on. Also, there were no advanced materials such as steel and building arch bridges out of stone was common.

The implications of arch bridges being built was the ability to create aqueducts that could bring water to cities and to create roads and bridges that could be used to transport goods and people more easily. The Romans built many arch bridges throughout Europe, Asia, and North Africa which greatly benefited them in creating and maintaining their empire.

Physics Involved

The abutments prevent the footers from pushing outwards. The keystone sides must be sloped to allow the keystone to slide down, pushing outward. The force of gravity is distributed from the key stone throughout the bridge, locking everything together.

If we assume that the mass of a bridge is 200kg we can find the force of gravity acting on that bridge.

Fg=mg

Fg=(200)(9.81)

Fg=1.96x 10^3N

In Newtons Third Law we learned that for each action there is an equal and opposite reaction. In this case with the bridge, the force of gravity (Fg) is pushing down from the key stone to the abutments. The ground pushes back on the abutments creating normal force (Fn) which is equal and opposite to the force of gravity. This creates a resistance which is passed from stone to stone. It eventually pushes on the key stone which is supporting the load. Arch bridges are always under compression. In physics 11 we haven’t covered much compression or tension but basically the force of compression is pushed outwards from the key stone along the curve of the arch to the abutments. The curve of the arch and its ability to dissipate the force outward reduces the effects of tension underneath the arch. The greater the degree of curvature (the larger the semicircle of the arch), the greater the effects of tension on the underside.

If a horse and carriage were to cross such a bridge, they would exert their force of gravity through the bridge (key stone down to the abutments) and the normal force would push back, holding the bridge together. This makes the bridge secure and efficient for crossing bodies of water, valleys, etc.

Design and Building Process

On day one we started out with 4 orange tubs of play do, 1 blue tub, and a container of toothpicks. We spent the class making “bricks/stones” as that is what shape was common for creating arch bridges. A difficulty we encountered was trying to make them all the same size and shape as one another.

Thursday we continued molding our play do into bricks. Friday we made our first attempt at building the bridge with the amount we had and we realized it was quite difficult to stack the play do bricks. We ended up using the toothpicks, placing 5 play do bricks on each toothpick and then tried making the bridge again. We didn’t have enough however to make much of the bridge other than the abutments so we planned to buy more play do and toothpicks over the weekend.

Over the weekend we got 3 more tubs of orange play do and 2 more tubs of blue play do. We made some more bricks and flattened out the blue play do to make “water” underneath the bridge. We used the fresh play do for the abutments so they would stick better and be a sturdier base and started stacking the dried out play do on top. I thought of rolling up a piece of paper as the frame of the arch while we tried to balance the bricks and put a key stone in but it was quite difficult. We tried many times to stack, balance, and place the bricks the way these bridges were made but I believe we chose a poor material to make the bridge out of and that this affected our construction of the project. We ended up laying the bricks across the opposite way to make the “arch” and it looked like more of a doorway shape than an arch.

If I were to re create this project I may have used stones, wood, or another material to make the finished product more accurate to what arch bridges look like. Also, we should have prepared better by researching the history of the arch bridge first to get a better understanding of how they were constructed and the key steps to creating one. Nevertheless, I now have a better understanding of this invention and why they were efficient/stable ways of transport. I also gained knowledge of the physics involved in the arch bridge, although it took a lot of research, I now realize that it relates back to previous concepts in this course. This project helped me apply my learning to a real life invention involving physics and reminded me that physics is everywhere, you just have to think about it!

Resources

https://science.howstuffworks.com/engineering/civil/bridge5.htm

https://www.britannica.com/technology/bridge-engineering/Roman-arch-bridges

http://www.historyofbridges.com/facts-about-bridges/arch-bridges/

https://engineeringrome.wikispaces.com/A+look+into+the+longevity+of+Roman+Engineering

http://www.warwickallen.com/bridges/ArchBridges.htm

 

Narrative Essay

Physical Awareness

Lying on the spiky turf field, screaming in pain, I knew this could be the worst day of my life. The rush playing soccer gives me is indescribable. People at this age are getting bored of their childhood sports and activities, but never has the thought even come to my mind of taking a break from soccer, until I was forced to.

This season everything was going right. I was the co-captain, meaning I got the privilege of being the leader of my team for half the season. My first game was on October 16th 2016. It was a cloudy fall Sunday and we were playing Burnaby on our home field at Gates Park. My position is usually center midfield because I am a passer, though a few of our forwards were missing, so I volunteered to play as a forward that day. We were up 1-0 and there was about 10 minutes left in the game. We had a fast break and someone hit it up to me on the right side of the field. I controlled the ball and started sprinting up the side of the field when I saw out of the corner of my eye an opposing player running up on my left. I knew I had to pass the ball before the girl took it from me. Seeing no one in front of me, I made a sudden stop and turned. I heard a pop as if someone had jumped on a piece of bubble wrap or like listening to 100 knuckles cracking instantly. I collapsed to the ground, screaming as I experienced the most excruciating pain I had ever felt. Lying there, I knew I had torn my ACL, an athlete’s worst nightmare. Of course I didn’t want to believe myself. You hear all these awful injuries yet you never believe you will experience one, until you do.

After being carried off the field by my coaches, I tried to convince my parents to let me stay and watch the game. They soon saw that my knee was swollen up like a balloon so we rushed off to the hospital. The hospital trip gave me a bit of hope after they took a few X rays, gave me some crutches, and sent me on my way saying, “Go see a specialist if it still hurts in a week.”

Crawling into bed that night, I placed my knee on the bed and shifted my weight onto it, causing a shooting pain from my thigh to my ankle. I plopped down onto the bed, unable to stifle my cries, my mom came running into my room to say, “I don’t care what that doctor said, we are seeing a specialist tomorrow.”

I soon discovered I needed an MRI, which was quite an uncomfortable experience. I was placed on a cold hard table with a thin pillow under my head. My knee was held tightly in place by two foam cushions so that I couldn’t move it. The woman technician put headphones over my ears and, from a smaller room, pleasantly ordered me to hold still every 30 seconds. Hearing the loud buzzes and beeps made a shiver run up and down my spine. After what felt like a decade, I was finally free of the contraption. Then the wait for the results came.

It only took a week, but getting asked by everyone at school what happened to me was tiresome. The day finally came when I was informed of the worst news possible, I had torn my ACL and I needed surgery. I could not play soccer for over a year. The tears caused by the pain of the event will never amount to the ones that ran down my face that day. It’s like the one thing that defined who I was, was taken away from me.

So we set a surgery date right away. It was on January 23rd 2017. I refused to cry that day, as it was the first step to gaining back my passion. I showed up at the hospital and was asked to kindly put on a gown where my backside would be shown: lovely. A nurse then walked me down to the surgery room. As I walked in, I was blinded it was so bright. There were 7 people in it, which was when it really hit me that this was a “major surgery”. Trying not to focus on the numerous tools around the room, I walked over and laid down on the chilly metal table as the doctors started surrounding me. One man placed a mask over my nose and mouth. I thought to myself I don’t feel anything, why isn’t it doing anything? I soon started questioning the craziest things like, Did I actually hurt my knee? Am I in surgery right now? And then they just kept getting weirder, What even is Earth? Am I a girl? What is a girl? A nice woman doctor grabbed my hand and said, “Squeeze my hand Zoe.” Another doctor told me, “You’re going to feel a little poke Zoe,” as he put the IV in my arm. Then I was out. I had no dreams, no sense of time, I didn’t even see black. I just woke up in a different room. It was the most surreal day I had ever experienced.

Since then, I have been working on the strength of my legs every day and counting down the months until I can play soccer again. Being able to do more and more activities as time goes by is like unwrapping presents throughout the year. I was recently just cleared to jog again and it made me feel radiant. Something I learned from the whole experience is to appreciate everything my body can do. The little things like running and jumping bring me so much joy now and I will never take them for granted again.

 

2 things I did well:

I created detail through imagery, showing the story instead of telling it. I had no spelling, grammar, or punctuation mistakes.

2 things I could do better:

Cutting out dead wood would have improved my writing on this assignment as well as naturally stating my purpose.

“The Watch” by Elie Wiesel

As I walk in it is humid, hard to breathe but oddly cold at the same time. A scent of musk like a pair of wet socks hanging above. Prisoners smell like they haven’t showered in months and look like they haven’t eaten in a decade. Quiet sweeps through the room like a ghost causing a chill. The odd stomach grumble carries through the room. I assumed that as I walked in there would be children crying, but there are no tears left to run. Rows upon rows of skeleton-like men. There is nothing left to hide from others, no modesty. They’ve been stripped of themselves, all of them the same.

Elie Wiesel, Holocaust Survivor and Author, 87

Which To Kill a Mockingbird Character Are You?

Jem Finch

Do you protect your family against all odds? Are you afraid to disappoint your parents because of how much you idolize them? Are you faced with difficult decisions because you are both immature yet responsible at the same time? If so, you should be proud to say you are like Jem Finch. Someone who used to think courage was being able to complete a dare or to be a good shot; but he soon learns from his father and the events around him that it is so much more than that. An example of Jem being responsible is when his friend Dill runs away from home to Jem’s house, Jem says “You oughta let your mother know where you are” and makes the difficult decision to involve Atticus. After that, Scout and Dill become mad with Jem but he knows what he did was right. Jem is a person that will make sure everyone is safe and sound.

Scout Finch

Are you stubborn as heck yet still an insanely cute and innocent person? Do you find yourself to be very observant and constantly questioning the world around you? Are you unafraid of the stereotypes towards you and just continue to be who you are? Do any of these ring a bell? Scout hears countless times that she “needs to be more like a girl” but doesn’t let it get to her head and continues to act and dress the way she wants. Scout’s stubbornness is shown when she refuses to go to school because of her teacher who doesn’t like the fact that Scout is ahead of the rest of her class. Scout is very curious and asks tough, politically incorrect questions. Since she is young, she asks these out of complete innocence, not meaning to offend anyone. Scout is someone that would fight tooth and nail for you, literally!

Dill Harris

Are you not afraid to tell a lie? Do you like taking risks all to be with and have fun with friends? Do you like to make up stories to impress others? Dill loves adventure. Doing things that make the hairs on his neck stand up is what he lives for. Being friends with Jem has probably kept him out of a lot of trouble. When he visits Scout and Jem in the summer, he always has a story to tell, whether they are true or not. Overall Dill is a fun and kind friend to have.

This Chain Restaurant Will Link You and Your Friends Together

There are countless perks to eating at the Earls restaurant in Port Coquitlam. Earls is exceptional for any occasion. The minute you step foot inside you are greeted by a polite hostess who will ask you “which area would you like to sit in?” Whether you choose the dining area or the lounge you are guaranteed a comfy seat with plenty of elbow room. Once seated, a server will stop by to welcome and hand you a menu filled with everything from seafood to a wide variety of comfort foods and more. Then you are left with your tough decision because of all the drooling worthy choices. On most occasions I will go for the grilled to excellent Cajun chicken cheddar sandwich with the perfectly crunchy seasoned fries on the side. It is a great option for lunch or dinner. Another dish you may want to sift out is the prawn and pesto pizza that has a perfect crunch as well as a great flavour combination. Once you have decided, you can enjoy your time with friends, family, or date while you are amazed by the chefs in the back flipping pizzas and throwing them in the enormous pizza oven. Being able to talk to the people joining you is an important component for me. With the atmosphere being a perfect volume, it is a great place to talk to and get to know someone better. The scent of other guest’s sizzling eats surrounding you only make you more eager to get your own. As you think you are just about to fall off the edge of your seat, you see your server with your steaming plate of gorgeous food strutting towards you. Then you take your first bite. It will feel like July 4th in your mouth. It will only get better as you scope out the dessert menu. My number one choice is the tangy key lime pie with the crumbly graham cracker crust. Having my birthday dinner at Earls with my friends last year was special to me because I was spending the occasion with friends and sharing the delicious food. Once you have relished your meal and time spent with loved ones, you can pick up your pretty penny bill and be filled with not a drop of nostalgia. Leaving with a satisfied stomach, you know you will pay Earls another visit in a lickety-split.

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The Things We Did Not Eat

Immigrant Journal & Reflection

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I believe I made an interesting and lengthy story that had lots of cliff hangers. Something to improve on would have been researching more for historical accuracy. I liked the project because it’s something I haven’t done before in socials and it gave me a better perspective on immigrants and their hardships. I wish that I had started the project earlier on so that I could have worked through it slower, rather than trying to rush it a week before.