Review Question #22

CIRCUITS

To start out with, I will explain what a DC circuit is. DC stands for direct current, and it is the type of circuit that has constant voltage, constant current, and resistors. An electrical circuit will be connected by wires, and the current will travel through these wires. I will now explain the different types of DC circuits.

Here is an example of a series circuit.

In this type of circuit, the current is the same at all points along the wire. This is proven by the equation, IT=I1=I2=I3. This makes sense because the current only has one path to flow through, therefore it will be the same. Also, in a series circuit, the voltage drop across the entire circuit is equal to the sum of the voltage drops in the circuit. This is shown by the equation, VT=V1+V2+V3.

Here is an example of a parallel circuit.

In this type of circuit, the total current is equal to the sum of the currents throught each resistor. This is because the electrons are able to flow through a new path created by each resistor, in other words, there are two or more different paths. This is proven by the equation IT=I1+I2+I3.In addition, the voltage drop across each branch is equal to the voltage of the source. VT=V1=V2=V3 shows this concept.


Here is an example of a complex circuit.

In this type of circuit, finding the current involves the equation I = V/RE. First, find the equivalent resistance of the different parts of the circuit need to be found. Then the sum of those resistances will be the equivalent resistance of the entire circuit.To find the voltage drop of each resistor, it is necessary to use the equation V=RI, but you need to plug in that specific resistor's resistance and total current. Also, sometimes you can use V2=V3=VT-V1. This is used to find the voltage across each resistor in a parallel circuit.


I hoped that this posting has helped you to gain a complete understanding of the fun filled circuit world!

WHERE IS THE STEM REALLY ?

In this picture, the stem of the flower appears to be out of place. This is caused by the refraction of light rays. The light rays which produce an abnormal image are the ones that travel from the underwater portion of the stem through the water, across the boundary, in the air, and to the human eye. The light rays refract at the boundary. The human eye will see this distorted image because the brain sees the location of the image as the same location where the refracted or reflected rays intersect. So to the brain, the location of the image is where the refracted or reflected rays intersect with each other. The brain and the eye assume that light rays travel in a straight line and extend backwards until they get to the point where they intersect. However, the light rays from the part of the stem under water intersect in a different location than the location where the light rays from the part of the stem above the water do. This is what causes the human eye to see the image as it is.

Einstein's Quote

I chose the quote "Nothing that I can do will change the structure of the universe.
But maybe, by raising my voice, I can help in the greatest of all causes
-- goodwill among men and peace on earth." The reason I chose this quote is because it inspires me in so many ways and has a very deep meaning to it. It is saying that the world will always be the way it is. There will always be the rich, the poor, the kind, and the greedy. However, by raising one's voice, a great change among mankind could be made. It doesn't matter if you only change one person or the whole human population. Either way you are making the world a better place whether it be a small change or a big change. Having the courage to raise one's voice is though, but by doing so a positive impact can be made. If anyone ever tells you that you can't do something, you should prove them wrong and show them what you are really capable of. By doing this the world can become a more imaginative place instead of a place that is limited to knowledge and facts. Helping the world to become a better place will lead to world understanding and peace. The saying "nothing is impossible" also has to do with the message Einstein is sending. Although some people may give up, the people that keep on trying and working hard will continue to prosper. Just tell yourself that it doesn't hurt to keep on going, but it does hurt to give up. This is the main message that Einstein is conveying to people around the world.

The Physics of Speed Skating

This is Team 4's glogster. It will teach you about the basic rules, history,equipment, and physics of speed skating. Also, it has the three winners from the 2010 Winter Olympics from Vancouver. Enjoy!!:)

ENERGY

Although the energy unit has been short, we have learned a lot during the little time we had. We first learned about energy flow diagrams. These diagrams explain the flow of energy to different types of energy storage of an object. We also learned about the different types of energy storage. There is elastic, potential, gravity, internal, kinetic, and dissipated. In an energy flow diagram we identify the initial energy storage and the final energy storage, and also the system. For example, if a car was initially stopped at the top of a hill, and started moving down the hill, the initial energy on the diagram would be gravitational, then towards the end the car would have more kinetic some gravitational and a little bit of internal. No matter what type of movement or forces an object experiences, the initial and final energies will remain the same, therefore, energy remains constant and is conserved. There are three different ways that energy can be transferred. Work, heating, and electromagnetic radiation. When energy transfer has to do with forces causing displacement, work is being done. The equation for work when the force and displacement are parallel is W=Fx (work=force*displacement).When the work and displacement are not parallel then W=Fx*cos theta. Work is also a scalar quantity, so there is no direction associated with it. Another way to transfer energy is when there is a difference in temperature between the object and its surroundings, when this is the case, the energy in the warmer substance transfers to the colder substance. For example, when you are outside the sun transfers energy to you, causing you to be warmer. Next, power is the rate at which work is done. Power can only be calculated when the force is constant and is parallel to the constant velocity. We have also learned how to calculate the amount of energy be transferred. Energy is always represented in the unit of Joules (J). An object experiences kinetic energy when it is moving, and the formula for kinetic energy is KE=1/2mv^2. Also, potential energy can be found by using either PE=mgh or PE=1/2kx^2. We also, learned about mechanical energy, which I thought was more difficult. Mechanical energy involves the sum of all the types of energy a body experiences. This is when you would set the initial energy equal to the final energy because energy remains constant throughout an object's path. I have really enjoyed this unit because it is so different than anything else we have done. It is really easy for me to make connections with this to the real world.

What I have found difficult about what we have studied about energy is finding the different speeds and types of energy an object is experiencing through its track of motion. For example if a roller coaster starts at the top of a track, it has potential energy, and as it continues downward it has kinetic energy and may still have potential energy. Also, the original energy is equal to the energy an object has later in its path because the energy is conserved, therefore to find something such as velocity you can set the original energy equation equal to the energy equation that the object is experiencing later. Out of everything we have studied about energy, this is what I have found most difficult.

My problem solving skills have been good, but I believe that they can be better. When I see a problem, I have to think about the information I have and the information I don't have and find the equation(s) that will help me reach what I am trying to find. However, once I organize my thoughts on how to solve the problem, it is easy for me to figure out the answer. I believe with more practice, solving energy problems will be a piece of cake!

Energy is not just a boring topic that we learn about at school, but it applies to our daily life in many ways that you would never even imagine. If you are riding a roller coaster at an amusement park, there is mechanical energy because the amount of energy stays the same throughout the track, but there may be different types of energy along the track. For example, if you start at the very top of the track with potential energy, and start to move downward with kinetic energy, the potential and kinetic energy would be equal to each other because the energy is conserved. Also, when you drive to school every morning, the tires create friction with the road. Therefore the car and the road will gain a little bit of internal energy (friction). As you can see, energy is everywhere even if you can never see it.

Attribution:
Physics Class Notes

THE ELEVATOR PROBLEM

When you go in an elevator, you might feel that all you blood rushes to your toes. You might also feel like you are being pulled up. This all has to do with elevator physics. If you stand on a scale while you are going up and down an elevator, you will notice that your weight on the scale will change as you move up and down and change direction.My question is If you are standing on a scale in an elevator, why does the scale read different numbers as you move up and down at different speeds? My glogster will explain why this happens.

Circular Motion and Gravitation

Although grasping the concept of circular motion and gravitation can be difficult, I learned many new things about physics. When an object is in a constant or uniform speed traveling in a circle, the object is in uniform circular motion. Also, the distance and object travels around a circle is the perimeter. One complete revolution around the perimeter of a circle is the circumference. The equation 2*pie*r represents the circumference of a circle. In addition, the speed of the object in uniform circular motion is given by v=2*pie*/T m/s. Period T is the variable for the time it takes for the object to make one full revolution around the perimeter, and it is given in seconds. Also, the frequency is the number of rotations per unit of time an object makes around the perimeter, and is given in Hertz, abbreviated as Hz. Therefore, T=1/f s and f=1/T Hz. Also, objects moving at a constant speed don't have a constant velocity. This is because an object in uniform circular motion is constantly changing direction. However, the magnitude of the velocity of the object will remain constant. Tangential is best used to describe the direction of the velocity vector of an object while in uniform circular motion. Furthermore, when an object changes direction, it accelerates. This acceleration is called centripetal acceleration. Centripetal acceleration means that the acceleration will always be directed towards the center of the circle.  Another fact is that the acceleration will always be perpendicular to the velocity. In addition, centripetal force is the force that must be applied to keep an object moving in a circle. The centripetal force is not a force by itself, but the centripetal force is provided by the force that keeps the object in a circle. the equation to solve for the centripetal force is Fc=mv^2/r N. When an object moves in a vertical circle at the end of a string, the tension varies with the position of the body. At the highest point the centripetal force equals Ft+mg=mv^2/r N. When it is at the lowest point Fc is found by Ft-mg=mv^2/r N. We also learned that Newton discovered that the gravitational force varies inversely with the square of the distance between two objects, which is called the inverse square law.  The Law of Universal Gravitation states that "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." Therefore the equation for the force of gravitation is Fg=Gm1m2/r^2 N. To find the acceleration due to gravity of an object of mass we can use Newton's Law of Universal Gravitation. The equation can be manipulated into another equation: g=GM/r^2. We have learned a lot this unit, but overall it has been very interesting.

What I have found difficult about what we have learned is the period and frequency. I constantly get confused and mixed up between the both. Also, I find it difficult to find the centripetal force requirement, especially when many forces are acting on the object.However, I feel that I can get confident in these areas of weakness if I keep practicing.

My problem solving skills are pretty good I would say. Sometimes I can make careless mistakes and not realize it. Other times the answer is right in front of me, but I just can't see it. The key to my success is practice because that is how I learn. It gives me more and more experience and prepares me to solve even harder problems in that area. If I continue to do this, I believe I can get better at problem solving.

Newton's Second Law

This is what I learned about Newton's second law...

Newton's second law states that the acceleration of an object is directly proportional to the net force, and indirectly proportional to the mass of the object. When I first saw this, I have to admit that I was very confused. However when I was given the equation F=ma, I understood the concept. "F" is the variable for the sum of the forces, "m" stands for mass, and "a" stands for acceleration. This equation is the foundation for a=F/m. The second equation is used to find the acceleration of an object that is under contact of a force. Now I understand this law thoroughly. An easy way for me to think about it is if someone pushed a ball across the floor with an applied force, then the object would obviously accelerate if you think about it. Also, if you pushed it four times as hard, then the ball would accelerate four times as fast. This thought made the law very clear to me. During this unit, we also learned about apparent weight. Apparent weight is the amount of force an object exerts on the surface it is on, where as actual weight is the amount of gravitational force that acts on an object. Another thing we learned was about friction."The friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it." There are two types of friction, kinetic and static. Kinetic friction occurs when an object is in motion, and static friction occurs when an object is at rest. We also learned about the coefficient of friction,mu. The equation is Ff=Fn*mu. We have learned a lot about this unit, and so far it has been filled with fun!

What I have found difficult about what I have studied is when to set the sum of the forces equal to ma. At first, I was very confused about this, but I later figured it out: the sum of the forces is set to ma if the axis that the motion is occurring in is being involved in the sum of the forces equation, and the sum of the forces is equal to zero if the axis where the motion is not occurring is involved in the sum of the forces equation. I also was a little confused about when to find the sum of all the forces and when to find the sum of only the forces in the axis of motion. These two things were the most confusing for me, but it didn't take me long to figure them out.

I believe that my problem solving skills have improved tremendously. I am very efficient now, and I am able to tell how I can figure out various unknown variables in problems. I am also very comfortable with the FBDs and the new equations. Overall, I believe that I have gained more confidence in being able to solve problems.