Unite 3 Relfection

In this unit we started out by learning Newtons 3rd law: 

For every action there is an equal and opposite reaction. 

This is exactly as it sounds if I push you, you push me back with the same force I pushed you. For example imagine you hit a piece of paper, It doesn't feel like you hit it very hard does it. THat because the paper hits you can only hit the paper as hard as it hits back and the piece of paper doesn't hit you very hard. Now if you hit a punching bag, it would hurt because it hits you much harder than the piece of paper. 

In this unit we covered the following topics that pertained to Newtons 3rd law: 

Action reaction pairs 

How a horse pulls a carriage  

adding forces/vectors at angles 

Gravity and tides 

Momentum and Impulse/ Conservation of Momentum 

First lets take a look at action reaction pairs  

You see this book, it's just a normal book no tricks, but it is doing something very interesting, it's pulling the world up. Pretty amazing, as a matter of fact anything with has mass pulls at other things with mass. But how come we don't notice this book puling on the earth. 

As Newton said every action has an equal and opposite force.  This means that the book is being pulled by the earth the same amount of force that the book is pulling the earth. Now since the book has such a minuscule mass it doesn't really move the massive earth enough to be noticeable.  

Now say we put that book on a table

Now we have two forces acting on the book. the book pulls on both the earth and the table, but thankfully the table is strong enough that when it pulls on the book with an equal and opposite force it counteracts the earths pull and prevents the book from falling to the earth. 

Now that we know how action reaction pairs work we can ask the question: 

How does a horse pull a carriage? 

First off because of N's 3rd law we know that the horse exerts an equal and opposite force on the carriage and the carriage would do the same. So how does the carriage move? We also know that the Carriage has an equal and opposite force with the earth and that the horse has it's own equal and opposite forces with the earth.  

But, because the horse has hooves it is able to push on the ground much harder than the carriage allowing the horse to pull the carriage with some help form the earth.  

Adding forces/vector and angles: 

Lets imagine that the below picture is of a person being pushed north stream by a stung stream and he wants to get across to the left side. The stream is the green and the persons current trajectory is the red going right.

 North

South                             Southeast

If the person followed the red line he would end up down southeast of the shore (Quadrant 2 in the graph). But lets say the guy positioned himself the way the white arrow is and started rowing, he would end up right along the red lines path, just where he wants to go. 

Lets also imagine that the top of the green line has a force of 100 N's and the right side of the red line also has 100 N's. If we also imagine the two different lines represent the vectors of two guys pushing a couch then the couch would be pushed in the direction of the white line. and if we remember back to Unit two and adding vectors we would know that the couch is being pushed with a force of 141 N's.  

Gravity and Tides:

In this unit we learned that something with mass attracts all other things with mass and that Force depends on the mass of objects and the distance between objects.

Inverse proportional law: the farther you get from something the more squared it is ( the less force you it has on you). That means that person standing on top of a mountain would have less force pulling on him compared to someone standing at sea level

In order to find your force at any given time we use the Universal Gravitational Formula:

F= G m1m2/d2

We know that the moon exerts a force on the earth because it has mass. Because there is so much water on earth it is going to be pulled toward the moon, but it doesn't just get puled to one side of the earth. Lets say the moon is on side A and the force of earth on moon is 25 N. Next lets say

 that the opposite side of A is B and B pulls on the moon with a force of 5 N. The center of the earth is also pulling on the moon with a force of 15 N. If we were to subtract 25 and 15 we would get 10 and if we were to subtract 15 with 5 we would get -10. It's because of these two equal and opposite forces that we have tides on both sides of the earth.

The above diagram shows the spring and neap tides. A spring tide is where the moon and the sun
 are aligned with the earth making higher tides than normal. A neap tide is when the moon is not aligned with the earth and is generally a half moon.because it's not aligned witht e earht it doesn't give off as much force making the tides smaller.


Momentum and Impulse/Conservation of momentum.


Momentum is defined as P=MV
Impulse as J=F change in T

If we want to find the momentum of soemthing we just do the equation

Change in P= Pfinal- Pinitial

to find impulse

J= F change in T


 When things stick together

ptotal=ptotal after

or

MaVa+MbVb=Ma+b(Vab)


 When two objects hit there momentum will be conserved.

This is true because

Fa=-Fb
then
F change in Ta= -F change in Tb
 which equals
Ja= -Jb
 equals
change in Pa = - change in Pb

if we take Pb and move it to the other side we would get

Change in Pa + change in Pb= 0

so therefore mass is conserved.

An example of this in action would be two people throwing eggs at each other and the egg doesn't break. Why doesn't the egg break?

We know that no matter how the egg is stopped it is going from moving to not moving and therefor the change in momentum is the same regardless of how the egg is stopped.

P=MV
Change in P = Pfinal- Pinitial

Since the change in momentum is the same regardless of how the egg is stopped, the impulse is also the same regardless of how quickly it is stopped.

Change in P = J


The egg tosser stop the egg over a long period of time, since the impulse is constant the force on the egg is small. A small force on the egg means it will not break.

 

 

 

Difficulties

I found this section very hard mostly because of the amount of math in it. But I know that I can over come this by practicing, because that is exactly what I did in my math class and my scores are already improving. I already feel more confident in taking the test because of this blog reflection, I thin it really helps for me to right down everything I know in one place. My studding skills will definitely improve after this because I'll start to practice the equations more.

I hope to do better next unit by taking what I learn in class and in homework and working it over until I reach a deeper understanding of it.

Connections 

I think it's strange how everything pulls just a little bit on everything else with mass. Now I understand how scientist believe black holes are made, If everything pulls on each other and some little mass is taken away then I guess that creates an imbalance in the forces causing a massive vacuum.

Tide resource

This short video gives a great, simple description of how the moon and the sun effect earth's tides. The video's use of physical examples is very effective because it makes whole the thing a lot easier to understand.

Unit 2 Review

What I learned in this Unit. 

Newtons second law of motion: 

Acceleration is directly proportional to Force and, 
Acceleration is inversely proportional to Mass. 

                           OR 
                          
                          a= f/m

In vernacular this means that as acceleration increases force does to, but mass decreases.  To help us grasp this lets assume the perspective of a skydiver. As soon as somebody jumps out a plane his weight starts to bring him down to earth and he is at the top of his acceleration. As a person falls through the air he encounters air resistance which causes him to decelerate. But this does not mean that he is going slower, in fact he is actually picking up speed which causes more air resistance, which applies more force in the upward direction, causing the force applied by his body (the downward force) to decrease, in turn causing acceleration to decrease. The upward and downward forces will continue to level out until they are the same, at this point the overall force equals zero, which is found by subtracting the up and down forces. Because the overall force is zero it is no longer causing the skydiver to accelerate, at this point we can say the diver is at terminal velocity which is the fastest he will go. It is also important to note that the acceleration and force both equal zero. 

 What happens when a parachute is opened.

A parachute usually has much more surface area than a person, which causes the air resistance to increase. But it doesn't cause any old air resistance to increase, but the upward resistance. This means that the skydiver will go slower, but the downward force will still pull the diver down causing the up force and down force to even out and make the overall force zero. During all this new shenanigans the acceleration actually increases as the upward force slows the diver down. But as soon as the downward force starts fighting against the upward force the acceleration decreases until the person reaches terminal velocity. The velocity during all this decreases making the new terminal velocity to be slower than the old one.

How to calculate the distance of a falling object.

D=1/2g(t)^2

What happens to an object that is thrown up.


The ball first starts out at a certain velocity and keeps a constant acceleration of 10m/s^2 due to the force of gravity. As the ball moves up It decelerates until the velocity at the top is zero, but as it falls it begins to accelerate again and it's velocity increases.

What happens when something is thrown up at an angle.

When something is thrown up at an angle it has both a horizontal and vertical velocity. If a ball moving at a 45 degree angle is moving a speed of 50m/s then we can use the algebraic formula a^2+b^2=c^2 to find the horizontal and vertical velocities, but for this one we can say the horizontal velocity is 40m/s and the vertical is 30m/s because it forms a 3,4,5 triangle. Another common triangle is a 1,1,1 or 1.41. In order to find the velocity use the formula v=d/t. The velocity of the ball at the top of it's path is equal to the horizontal velocity.


 Formulas I've learned,

D=1/2g(t)^2     V=d/t    a=f/m


What I have found difficult about what I studied is

How to understand the underling concepts of the things we're learning, such as how a skydiver speeds up to increase his air resistance and how this causes him to start to decelerate. I also found it difficult to understand the homework which  would take me a while to understand or i'd just rush quickly through it without truly grasping a lasting understanding. Because of this I often found myself constantly asking my classmates how to do a problem because I wasn't sure how to find the answer. This was mostly problem  with the math part which is a hard subject for me. Although I knew I could find the answer I simply didn't have the confidence to try and solve it.

How I overcame these difficulties

I over came these difficulties by coming into Ms Lawrence and having her explain things more throughly. Her use of pictures (which may be tedious to draw, but worth it) really helped me conceptualize things, which helps me paint a picture of what is happening and gives me a deeper understanding of what is going on.  I also started to get more engaged in my homework, I started to take more time on the difficult problems until I understood how it worked. All of this just helped bring about multiple little lightbulb moments when concepts started to click and become clearer. As I started to understand things better I started to gain the confidence to ask questions in class that led me to understand the iffy subject because I addressed them right away.

Problem solving skills.

My skills started off pretty poorly. I would sometimes zone in and out of class I'd rush through my homework and I would rarely ask questions. Later on though this got a lot better as I started coming in more often and working as well as asking questions and paying attention in class. I think my persistence and effort is starting to pick up again, it troubled me how poorly I scored on my quizzes and my borderline grade. So i've really started to try and pick things up while also increasing my problem solving skills by doing the homework more throughly. I feel like my communication and writing skills are pretty good (excluding penmanship) and I think I work well in a group. One of my biggest problems is patience, I have plenty of it, but I  get agitated when I have a lot of work and try to rush through problems while understanding them at the same which sometimes reflects poorly on my work.

Goals for next year.

My goal for next unit is to participate better in class and work throughly on my assignments. I will do this by completing my homework, participating in class and trying to pay more attention.

Connections  

 Hitting a home run and skydiving are great examples used in this unit. But I also made a connection when last weekend I was talking to my parents about them visiting me. We talked about how long the flight would take to get form Saudi Arabia to Asheville. I later realized that an airplane taking off and landing is just a much more extreme version of the home run example, where it has both a horizontal and vertical velocity. Because the plane takes 16 hours to get 1,533.7 miles from the US to the middle east I deduced that the plane was moving at a horizontal speed of 96 miles per hour. My math might be wrong but if it is correct thats a little interesting, I'll remember this next time I run a marathon and finish in 5 hours.













This is just my groups video we did for newtons second law.

This video gives a good explanation of free fall by explaining that two objects will hit the ground at the same time, because they both move at the same acceleration.

Newtons 2nd Law resource.

This video gives an excellent explanation of Newtons second law. Though it is a little hard to follow in the beginning because it starts kind of in the middle of the video, but if you keep watching it'll get clearer. The video is also interesting because it provides the definition of Newtons Second law as force equals mass times acceleration which is simply another way of saying acceleration equals force divided by mass. It also states that this means that force is directly proportional to acceleration and mass is inversely proportional to acceleration.The use of a football kicker helps us understand the second law better by giving us a clear example that when force is exerted on an object it will accelerate.

First day questions.

What do you expect to learn in Physics this years?

I don't really know what physics is, but I think it has something to do with studying how the natural world works. So I guess we would study what friction is and how it slows down objects, maybe we'll even learn why and how tornadoes suck stuff up and throw it somewhere else. The atomic bomb might have something to do with physics so we'll probably learn about how that works and we could possibly compare how chemistry and physics relate.

Why do you think studying Physics is important.

Physics is still a new subject to me so i'm not one hundred percent sure why we need it, but I think it has something to do with studying how the natural world reacts with itself. I know its effected our lives by discovering things like gravity and lightning. I also hear a lot about physics and space so it might play a big part in human space exploration and I might be confusing this for chemistry but I also think physics played a part in discovering the Higgs boson which explains the properties of matter and its mass.


What questions do you have about Physics

What is Physics, I hear its a huge subject that is extremely important and overlaps with other science disciplines  often. Why is it so important what does it do and why do I need to take a class on it, those are my three main questions.

What goals do you have about Physics this year

 My main goal is to master physics. I want to be able to know the basic principles of physics and be able to explain it to somebody else. If I can explain it to somebody in an easily understandable and coherent way then I would have developed a deep understanding for this course. Grade wise I would really like to stay above and A and maybe even move up to honors.