# View all posts by alexism2015:

## Wave interference

How do noise cancelling headphones use wave interference to eliminate unwanted sound?

Active noise control uses sound wave interference to reduce sounds . Outside noises are captured  through a microphone where a sound wave is emitted with the same amplitude but inverted. This cancels the wave out removing the noise.

1. Constructive interference: the crest or trough meets with another pairing crest or trough where the energies combine. The energies combine to create one big trough or crest by passing through one another and only have an affect where they meet.

2. Destructive interference: when an opposing crest or trough meets with the opposite wave, the energies combine by canceling each other out. The energies pass through each other and only have an affect where they meet

3. Standing wave: When passing waves have the same amplitude and wavelength resulting in the interference pattern becoming stationary.

## Newton’s Law Video

Newton’s First Law

Considerations: If there are unbalanced forces present the object will not continue in the same path of motion. Jaya stood in the way and applied a strong enough force to stop the moving cart. Even if Jaya wasn’t standing in the way, the cart would have eventually slowed down due to friction between the wheels and the floor.

Newton’s Second Law

Newton’s Second Law is built off of the First Law. It states that the acceleration of an object due to unbalanced forces will depend directly on the unbalanced force (referred to as net force) and inversely on the mass of the body. In other words, the more mass an object has, the more net force is needed to cause it to accelerate. The formula for Newton’s Second Law is a=F/m, where F is net force, a is acceleration, and m is mass.

Considerations: There was a force of friction between the wheels and the floor. This would cause the cart to slow down quicker for each situation separately. There is also friction present between the wheels and the surface of the cart; since each cart is only supposed to support one person. This would cause the cart to slow down much quicker in the second situation.

Newton’s Third Law

For every action, there is an equal and opposite reaction. This can be represented by the equation F1 = F2, or m1a1 = m2a2, where F=force (N), m=mass (kg), and a=acceleration (m/s2). In this example, the cart is pushed towards the wall, which it then hits. Upon impact, the cart is pushed backwards due to the equal and opposite force being exerted from the wall.
Considerations: In ideal conditions, this cart would rebound off the wall with the same amount of force as it hit the wall and continue going in the opposite direction forever. However, this is clearly not the case because the cart does not travel at the exact same speed directly back to the pusher. This is due to the force of friction between the wheels and the floor acting on the cart after the point of impact with the wall, and potentially the inability of the wheels to quickly change direction of rolling. Also, if the wall had any elastic properties, the cart would experience less force on the rebound become some of the initial force would be absorbed by the wall.

## Darwin and DNA

How did the discovery of DNA prove that Darwin’s theory of evolution was correct and how does it change the way we view evolution today and into the future?

Darwin’s main points from his evolutionary theory included the diversity among animal groups that trace features and genes back to a common ancestor. Like how humans with arms, legs, and posable thumbs can be related to ancestor fish. Darwin also believed in the theory of natural selection and how species that evolved from a deep water fish died out as they proved unfit.

Species also have Have variations from one another depending on where they are found. For example during Darwins trip to the Galapagos islands he noticed the upper shell on the tortoises differed from one another depending on which island they were placed on. The shells differences benefitted the turtle’s in different ways depending on their habitat around them. Darwin believed this to be adaptations caused by the animals fitness in relation to these surroundings. We now know know that certain genes in DNA have mistakes like deletions, additions, and mistakes which alter the way things are made. Also the use of gene switches control the gene turning it off and on, controlling how much of the gene was made or how little. In the future adaptations like the turtles will still happen forming around their ecosystem and their needs

Only a few mistakes in the genetic code can create great differences that separate species. For example humans and chimps have only a one percent difference in their DNA sequence. That 1% creates lots of different adaptation that can sometimes benefit that species. Like the difference between chips and humans would be in their jaws. Animals have less muscle in the job bone rather chips have more. The extra muscle in a job allows them to eat harder more difficult food while the lack of muscle creates cranium space for humans which allow their brains to grow for about 30 years of their life. Another analogous similar feature in species would be legs. Legs were found about 365 million years ago on fish. These four legged fish fossils have the same bone structure found on four legged animals today.An example of this would be the extinct animal Tiktaalik. This animal had an ideal form. It had the body of a fish with the bone structure of four legged animals. In thousands of years from now we will still have the bone structure of four legged animals, but could fly around.

## Week 17 in Precalculus

This week in Precalc 11 we learned a new trigonometry formula known as the sine law. Sine law is used to find the angles and side length of triangles that don’t contain a ninety degree angle. To use this formula you need 3 pieces of information, 2 of which must correspond to one another. For example if you have angle C you need the side length c.

The equation you can use for sine law is:

The equation for sine law can be reciprocated depending on what you are trying to find. If you are looking for an angle, you would put the sin’s in the numerator and the side length in the denominator. Vise-versa with finding a side length.

When solving with sine law, you must choose on fraction that has a completed numerator and denominator and another fraction that has either the numerator filled out or the denominator.

Then you must isolate the variable. To do this you have to get rid of the uncompleted fractions denominator and you also must get rid of the trig function attached to the variable on the numerator. To do this you must take sin and inverse it. For example:

## Narrative Essay

Two things I did well:

1. Sensory detail and descriptivity

2. Creating a story that accurately represents everything I wanted it to

Two things I can improve on:

1. Quote intergration

2. Reading over carefully to catch little mistakes

## Opinion Piece

Sticks and Stones
Contrary to popular nursery rhymes and sayings, words leave marks as deep and painful as sticks and stones. A word with no more than one syllable can silence a room and exasperate a culture using less than a breathe. If these words cause so much harm then why would we use them? Teams such as The Cleveland Indians, Chicago Blackhawks, Washington Redskins, and Edmonton Eskimos are all examples of taking words commonly used to appropriate a culture, and turning them into entertainment. Words such as Redskin stem all the way back to 1769; not only was it used as a derogatory term, it was used to describe the torturous scalping and skinning opposed onto the First Nation. Today the word is used to describe a football team which has won three Super Bowls; this team is depicted by a drawing of an Indian chief wearing a head dress with feathers, and cheerleaders who wear long black braids. Not only is the word connected to a dark past, they are portraying the Native Americans stereotypically. Many Aboriginals, including, Susan Harjo have filed a petition against the Patent and Trademark Office asking for the revocation of the team’s six federal trademark registrations, because of the disparagement upon the community. However, with the many people petitioning the court no change was made until 2014. With this being said, studies show that seventy-three percent of Native Americans were not bothered with the word, “redskins,” and only twenty-six percent were bothered by the use of Native American imagery in sports. Furthermore, the aboriginals have no doubt been through hardship, but it is not over for them; the issue of sports teams seems rudimentary to the trouble which faces their reserves. Most people wouldn’t think about the burdens they face; in their minds Natives live off the land with buffalo skins and spears. These perceptions, these stereotypes, drive from the medias notion of their culture. They see The Cleveland Indians, Chicago Blackhawks, Washington Redskins, and Edmonton Eskimos versions plastered on their uniforms, merchandise, and billboards, but they don’t see the truth. They don’t see who chief Blackhawk really was, and what war he fought in. They don’t know that Eskimos are really known as Inuits and that just because they don’t look like Pocahontas doesn’t mean they’re not indigenous. As Winona Linn once said in a spoken word: “ He could only call me out because of the colour of my skin but my skin doesn’t match his perception of Indian,” ( Linn, 2013) because they only see the transparent mask put upon their culture. If you were to replace the derogatory terms or crude cartoons with any other culture, light would shine upon the immorality. Light would shine on the sticks and stones.

Shapira , Ian. “A brief history of the word ‘redskin’ and how it became a source of controversy.” The Washington Post, WP Company, 19 May 2016, www.washingtonpost.com/local/a-brief-history-of-the-word-redskin-and-how-it-became-a-source-of-controversy/2016/05/19/062cd618-187f-11e6-9e16-2e5a123aac62_story.html?utm_term=.29f3f591d492.

“Poll: Native Americans’ attitudes toward the Washington Redskins team name.” The Washington Post, WP Company, 19 May 2016, www.washingtonpost.com/apps/g/page/mobile/sports/poll-native-americans-attitudes-toward-the-washington-redskins-team-name/2034/.

## Week 16 in Precalculus

This week in Precalc 11 we learned how to multiply and divide rational expressions.  The General rule for doing this is:

1. Factor (numerator and denominator)

2. Use exponent laws

3. Cancel out like terms

this process is much like cross multiplying, for example:

since these fractions can get pretty long and “ugly”, writing them out is helpful and easier to manage. If you follow the 3 main rules as well than solving is much more efficient.

Monomials are easier because you can combine the numerators and denominators than simplify.

When it is a single variable expression you must factor in order to simplify. You can only cancel out EXACT terms. The + or – signs act as unpenatratable glue. They connect the numbers on either side of the sign, acting as a package.

To cancel out you can use the cross multiplication technique. Then combine the leftover numerators and denominators.

The last thing you must do, which you actually do first, is find the non-permissible values. A non-permissible value is the numbers which make the denominators equal to zero. You find these once you have factored.

## Week 15 in Precalculus

This week in Precalc 11 we learned about equivalent rational expression. Rational numbers are quotients of two integers. So, two polynomiales are known as rational expressions. E.g:

to simplify a rational expression the first thing you must do is find the non-permissible values. A non-permissible value is a number which makes the denominator zero because, you can not have a fraction with a zero as the denominator.

To find this value you must find the zeros meaning figure out what numbers would create the equation to become zero. You can do this by inspection or factoring.

After you you have figured out the non-permissible values you can then cancel out common factors. These factors must be the exact same in order to cancel out.

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