## Wednesday, May 19, 2010

### Reflection: Electricity

DC Circuits:

Direct Current is when electrons flow continously from a positive to a negitive area through a conductor. A DC circut is made up of a generator(a powersource), a conductor(like a wire), and a resisotor( the place the energy is used). All DC circuits have a constant voltage and current. There are three types of DC circuits series, parallel, and complex these are explained below.

Series:
In a series circuit because there is only one path to follow the current is the same throughout the entire circuit. However the voltage drops while going through the resistor. The voltage drops are added up the will equal the total voltage.

Parallel:
Parallel circuits have multiple resistors, this means there are many paths for the current to flow down. The total current is the sum of each resistor's current. Resistors in parallel circuits have equal voltages, all voltages are equal. The amount of each voltage in each resistor equals the total voltage.

Complex:
Resistance in a complex circuit has to be found in multiple steps. First you would have the parallel resistance. Then add the the parallel resistance to each of the resistances of the other resistors. After this divide the total voltage by the total resistance to find the total current. To find individual voltage of each resistor multiple the total current by resistance in each resistor.

## Sunday, April 25, 2010

### You Can't Defy Gravity!

Before starting this project I was advised to take a picture of something pertaining to my favorite unit of physics. By this time in the year we had practically covered the whole book. Looking back through all of the chapters I realized that my favorite unit was the one covering forces. Forces were a board and extensive topic. Thinking of the picture I would take I tried to think of my favorite force. Finally I narrowed it down to gravity. Gravity is my favorite because it is a force you can’t change. You can have the tension force in one situation but not in another, gravity is always there a constant. But what situation illustrated gravity best, since it was everywhere. Finally I choose the very simple idea of throwing a ball into the air. My picture of a ball being thrown into the air has two forces acting on it gravity and air resistance. As the ball goes upwards and then downwards these forces are always acting on it. The earth is attracting the ball back towards itself. The weight of the ball times 9.8 m/s^2(the acceleration due to gravity) equals how much force is pulling the ball down. The second force, air resistance, is only there in a small amount, because the ball is small and not traveling at a high speed. Air resistance is working in the opposite direction of the object.

## Sunday, March 21, 2010

### Einstein Quote

"It's not that I'm so smart , it's just that I stay with problems longer ."-Albert Einstein

As I was scrolling down the page skimming over quotes I realized this post would be more of a challenge then I originally thought, not because explaining would hard but because choosing one quote seemed to be impossible. The one I choose was the most interesting for me because what he is talking about comes up in my learning process a lot. The most interesting thing I find about this quote is that one of the few geniuses is admitting that he is not all that smart.  Einstein contributes all his discoveries to a great work ethic. Now this is shocking because you would expect a genius to not only know that he is one but to gloat about being one. This part shows just how humble Einstein was, making him that much cooler. The second part I also really liked. Most student studies are about being able to plug-and-chug. We do not really need to read and understand what they are asking and why they are asking, all we need to know is how to identify variables and put them in a given equation correctly. When we do not get the correct answer we go straight to another student or teacher for help. I cannot speak for others but because of this my problem solving skills are not that good and I do as mentioned above a lot. Albert Einstein did more then just try find the answer as easily as possible and when he didn't he did not just give up. As he said he stuck with the problem. Einstein seemed like he asked himself challenging question and if the answer was not easily obtainable, he still stayed with that problem trying to understand everything about it. Over all I don't think he is saying that he is not a genius or he has made all his discoveries because of his work ethic but a combination of both. Einstein used both his work ethic and his natural talent for problems and one should not attribute all of his success to just that he was born a genius. To sum it up Einstein was not a lazy genius.

## Thursday, March 11, 2010

### LUGE

See my prezi about luge

## Saturday, February 20, 2010

### Energy

A) This past unit has been the one that I have learned the most from. To start off the unit I learned to use bar graphs as a way to show how energy is transferred. This concept provided a great base for the rest of the unit.  I learned the types of energy storage there are such as elastic, kinetic, gravitational, potential, and dissipated. And how different types of situation have different types of energy. No matter what situation or how much energy, the total amount of energy never changes. Energy can be transferred in many ways. Through work, heating and electromagnetic radiation. Work happens as energy is transferred by forces that cause displacements. When there is a temperature difference between an object and its surroundings the warmer object transfers energy to the colder. Electromagnetic Radiation is when an object absorbs light or loses it. When I make a graph I must show the types of energy in the original system and how it is transferred to different types in the final situation. To do this I must identify what is causing the energy change and then graph them. The difference between the the starting energy and the final one is change in dissipated energy. The process of transferring energy from one system to another is called work. Work measures the amount of change, i.e. change in velocity, in position, size, and shape, that a force produces when it acts on something. Work is a scalar quantity, work does not have direction. Work is equal to product of the force and the distance force is moving or W=Fx. Work can not happen if the distance and the force are perpendicular, no work can be done. The force and the distance must be in the same direction or at and angle(that is not 90 degrees).  Power, or the rate at which the work is done, happens when there is a constant force is parallel to a body in constant velocity. In this unit I have also learned how to how to calculate the amount of kinetic, potential or elastic energy an object has through simple equations such as KE=1/2mv^2, PE=mgh, or PEe=1/2kx^2. In the equation Pe=1/2kx^2, k is the force constant that measures the stiffness of the spring. I have also drawn on things from past units such as net force. The net force equals the change of energy of a body or W=changeKE=changePE. When I find the mechanical energy, that is the sum of all types of energy of a body. This unit is very different from the ones we have done in the past. I have had to learn a whole new set of equations and how to apply them. Usually in the past things have tied more closely to past units but in this unit's problems are vastly different from the ones in the past. How to use the new equations and these new problems have been the most difficult for me, I am not used to the types of things the question is asking me to solve for. Over all this unit was full of new types of problems, new equations, and new answers that I was uncomfortable with at first but over time they have become easier to understand. My problem solving skills have continued to become better. In this section I have had more challenging problems then ever, that I have worked hard to solve. I have tried to understand why I use a certain equation or why I I set PE equal to KE and not just try to get the problem over with as fast as I can. The problem solving strategy listed in the book has helped a lot with this problem.

B)Energy is major part in everyday life. We can see energy in roller coster rides at six flags, when the coster is at the top of the loop it energy is mainly potential, but as it goes down the ramp its energy is all or mostly kinetic. Or when a person is about to jump off a bridge with a rope around them all their energy is gravitational but at the end of the just it is mainly elastic. Or if you push an object across the room you are transferring from yourself to the object. Another example is with a bow and arrow, you transfer energy to the string which then transfers energy to the bow to travel through the air.

## Sunday, January 31, 2010

### Application: Glogster

Kinetic friction is when an object is in motion while static is while the object is stationary.  Using Newton's first law to find out why static friction is more than kinetic friction check out my glogster, click here!

## Tuesday, January 26, 2010

### Reflection Circular Motion and Gravitation

From this unit I have learned many things, I have learned new equations, I have come to better understand how/why objects move and have come to understand forces better. One of the first things we learned about were periods, these are a little tricky but help greatly in the problem solving procedure. They help with finding the velocity, in the beginning of the problem you are given how many rotations a minute or a second an object makes. You would then convert this to Hertz and then to seconds.

I have also learned about how objects move in circles. For example when an object is moving in a circular motion the velocity vector is tangential because it is always changing direction. The objects accelerations is always directed toward the center of the circle. So therefore in circular motion and objects acceleration is always perpendicular to it's velocity.

I have also learned what keeps the objects moving in a circle. To keep the object moving a centripetal force must be applied, this is not one specific force but rather could be any, i.e. friction of gravity. When objects move in vertical circles the centripetal force is different. Usually at the highest point of rotation the object centripetal force is equal to the force keeping the object in the circle plus the gravitational force then set equal to the mass times the velocity squared over the radius. At the lowest point the equation is the same but you subtract the gravitational force. But that is not always the case, depending on the way the forces are going you could have two equations for subtraction.

In some problems the forces are in different places. Problems that have to due carnival rides often have their forces in very different places, but still spin in a vertical motion. In these problems the firiction force can be in the upper y-axis and the normal force in the x-axis. Because of where the forces are you wouldn't necessarily solve the problem with the equations I stated above. You might do a sum of the forces in the y-axis or use the centripetal force equation. Overall there is no equation set in stone that you use to solve vertical circle problems. You have to evaluate your problem, draw an FBD, and choose that best method/equation to solve for with the facts you know. To sum it up the equations motions of vertical circles is different then horizontal ones.

I have also learned about universal gravitation. " Every object in the universe attracts every other object in the universe with a force that varies directly with the product of their masses and inversely with the square of the distance between the centers of the two masses" or the Law of Universal Gravitation sums it up perfectly. With this. This helps me figure out the what the gravitational pull between two object is or their masses or the distance between the two.I have also learned to find the acceleration due to gravity with any object.

This unit has been one of the most challenging for me. I have had to learn many new equations and how to use/when to use them. I have also have had to be very carefully with my fingers since I have been calculating big, long numbers. Again slowing down and reading the problem completely have lead to some mistakes in my work. I have also learned to make time in my day to review my notes even when there is not a test or quiz.

Gravitational problems have been hard for me because of the big numbers and to solve it is not also plug in the numbers but I have to go through steps or think about how to solve, that it is not just the given equation at the beginning of the notes.With this unit my finger skills have become much better. When I do not get a problem correct I check to make sure I have calculated correctly first.

My study habits have become better, with studying not just when needed. But as always my need to slow down and really read the problem has come into play. Also making sure I really understand the material and am not just solving the problem to finish it. I still need to work on things like slowing down, reviewing , and being careful in my work but I'm getting better with all of these things.

## Sunday, January 10, 2010

### Newton's Second Law

Newton's Second Law has been the toughest for me to understand out of the three laws. Newton’s Second Law helps us understand moving bodies by linking the cause and the effect (or force and acceleration) in a definite way. In the definition of Newton's Second Law it states that acceleration of an object is proportional to the net force and inversely proportional to the mass of an object. I found that very confusing until I learned the equations a=ΣF/m and ΣF=ma. These equations are the key to understand Newton's Second Law.  The equations and FBDs helped me solve problems that involved gravity, tension and applied force. After mastering the equations I came to understand how things are inversely proportional to each other.  For me though it was not just knowing when which equation or knowing what forces to use, but understanding why I would use each force/equation in a problem. This I think helped me get a better understanding of the second law. I may understand Newton's Second Law now, but I did have trouble mastering it. I have found a number of things difficult about the second law. One thing that I found hard was the direction the object was moving. If an object is moving upward the tension force (the force is usually tension) comes first in the equation. But when the object is moving downward the gravitational force comes first. In the beginning I did not understand this; I thought one force comes first no matter what. But after I came to understand that the direction the object is going affects the order the forces in the equation this problem was fixed. Another thing I had a bit of trouble with was inclined plans, I again had to refresh myself on SOH CAH TOA, but after that angles and inclined plans were a breeze. Just because I have survived this class for 1/2 a year does not mean I go without mistakes, my problem solving skills are stronger but not bullet proof (yet). I again have to remind myself to SLOW down. I have tendencies to rush through the problems as fast as I can. But I have gotten much better at slowing down reading the problem, thinking what I know, and using that information to solve. FBD's have been another small problem for me, in some problems I neglected to draw one. Since making many errors I have learned to make and FBD for every problem, even if not required to help. The making of an FBD helps show me how to set up my equation the right way.