Tuesday, February 19, 2013
Sunday, February 17, 2013
physics potential energy
This picture shows me going down a slide. When I was at the top of the slide I had gravitational potential energy. However, when I slid down, that potential energy was converted to kinetic Energy. If I had a mass of 27215.5 grams and I was elevated at the height of 6 meters, I could use the formula of PE=MGH to calculate the amount of potential energy.
Friday, February 15, 2013
Blog Reflection
Wow, these units are just flying by. The work and Energy unit went especially fast, but we learned many interesting and very helpful as the semester goes on. We began this unit by introducing work. Work is defined as the effort exerted on an object to change its energy. In particular Work is defined as Force x Distance and is measured in joules. To do work the distance and force must be parallel, so if walk down the hall carrying books, you do not do work on the books but if you lift the books you are doing work on them. Next we learned about power. Power is defined as the amount of work done per time required to do it. Its formula is Work Done/ Time. To compare work and power, take running and walking up the stairs. You do not do more work if you walk up the stairs or run up the stairs since both times you weigh the same and travel the same distance. However, if you run up the stairs you have more power since you do the same amount of work during a shorter time period.
The unit moved on to discuss mechanical energy. We first discussed potential energy. Potential energy is energy that is stored and held in readiness. For example a rock on the ledge of a cliff has potential energy. This particular potential energy is called gravitational potential energy because it is in an elevated position. It is measured by weight times height or PE=mgH. When the rocks falls, however, the potential energy is then converted into kinetic energy. Kinetic energy is the energy of motion. It is represented by the formula KE= 1/2 mv^2. The change of Kinetic energy is equal to the work, in fact.
Next We learned about the conservation of energy and machines. The law of conservation of energy states that Energy cannot be created or destroyed it may be transformed from one form into another, but the total amount never changes. So if there are a hundred joules of energy to begin, there will be a hundred joules of energy to end with, though some of it may be converted into heat. Machines manipulate the law of Conservation, by increasing distance to decrease the force required so that beginning work equal the end work. For instance, take the lever. The lever increases the distance so it requires less of a force to move the object. However, it is important to note that no machine can multiply work or energy. With this principle that egyptians built the pyramids, and Physics class was able to move a car!. However, with machines we concluded with learning about efficiency. It is very important to note that their is no machine that is 100% efficient which means that 100% of the energy input equaled the energy output. This is impossible so far because some of the energy is always converted into heat or thermal energy. You can calculate efficiency by useful work output over total energy input. '
All in all, this unit was gradually easier for me. I still struggle with understanding the mathematical reasoning of change in kinetic energy but I am getting better and better with it. I enjoyed this unit because it was simplistic in definitions and straightforward in formulas. I like how it all interconnected.
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The unit moved on to discuss mechanical energy. We first discussed potential energy. Potential energy is energy that is stored and held in readiness. For example a rock on the ledge of a cliff has potential energy. This particular potential energy is called gravitational potential energy because it is in an elevated position. It is measured by weight times height or PE=mgH. When the rocks falls, however, the potential energy is then converted into kinetic energy. Kinetic energy is the energy of motion. It is represented by the formula KE= 1/2 mv^2. The change of Kinetic energy is equal to the work, in fact.
Next We learned about the conservation of energy and machines. The law of conservation of energy states that Energy cannot be created or destroyed it may be transformed from one form into another, but the total amount never changes. So if there are a hundred joules of energy to begin, there will be a hundred joules of energy to end with, though some of it may be converted into heat. Machines manipulate the law of Conservation, by increasing distance to decrease the force required so that beginning work equal the end work. For instance, take the lever. The lever increases the distance so it requires less of a force to move the object. However, it is important to note that no machine can multiply work or energy. With this principle that egyptians built the pyramids, and Physics class was able to move a car!. However, with machines we concluded with learning about efficiency. It is very important to note that their is no machine that is 100% efficient which means that 100% of the energy input equaled the energy output. This is impossible so far because some of the energy is always converted into heat or thermal energy. You can calculate efficiency by useful work output over total energy input. '
All in all, this unit was gradually easier for me. I still struggle with understanding the mathematical reasoning of change in kinetic energy but I am getting better and better with it. I enjoyed this unit because it was simplistic in definitions and straightforward in formulas. I like how it all interconnected.
Sunday, January 27, 2013
unit reflection
The new unit began by introducing the new terms of tangential and rotational velocity and determining their differences. Rotational velocity is measured in rpm (rotations per minute) and measures the
amount of rotations an object has every minute. Tangential velocity is determined by distance over time. We learned real life examples of rotational velocity by with the carousel. Though all the machinery animals move at the same rotational velocity or rpm those who move on the outside have a larger tangential velocity because they have more distance to cover in the same amount of time. Also, we learned about the importance of rotational velocity and tangential velocity in train wheels, because the wheels on a train are tapered. If the wheels need to curve or self-correct, because the outer part of the wheel is smaller and on the outside, it will have the same rotational speed, causing the train to steer in swivels.
Here is a cool video that help explains railroad tracks!
Next we learned about rotational inertia. We defined rotational inertia as the tendency of an object to resist changes in rotation. It is dependent on mass and velocity. In particular, is is dependent on where the mass is located. Mass nearer the center or axis of rotation it decreases rotational inertia, and increases the ability to spin. That is why dancers pull their arms closer to their core when they spin.
After learning about rotational inertia, we learned about the conservation of angular momentum which is most easily explained through the formula Rotational Inertia times rotational velocity. Therefore, the momentum of a rotating object before is equal to the momentum of the rotating object after.
Next we learned about torque, or what causes the rotation of an object. Torque is determined by lever arm x force. Therefore, the larger the force or the lever arm, the more likely an object will spin.
Then we learned about Center of Mass, the average center position of the mass of an object, and Center of Gravity which is defined as the average position of weight within an object. In order for an object to be balanced its center of gravity must be within its basis of support or center of mass. Another way to increase stability is to lower your center of gravity or increase your basis of support. This is why wrestlers bend their knees and spread their legs when in a wrestling tournament.
Finally we learned about centripital force which is the center seeking force that pulls you into a circular rotation. When you are in a car and you make a sharp right turn, Centripital force is the only force acting upon you, your tendency to go in the opposite direction is not a force but inertia.
All in all, This unit required a lot of digesting, and some of the material had to resonate over a period of time before it sunk in (train wheels). I believe I should have asked more questions due to my problem was lack of understanding and lack of communication in this unit, but no worries. I think I grasped it in the end.
Here is a cool video that help explains railroad tracks!
Next we learned about rotational inertia. We defined rotational inertia as the tendency of an object to resist changes in rotation. It is dependent on mass and velocity. In particular, is is dependent on where the mass is located. Mass nearer the center or axis of rotation it decreases rotational inertia, and increases the ability to spin. That is why dancers pull their arms closer to their core when they spin.
After learning about rotational inertia, we learned about the conservation of angular momentum which is most easily explained through the formula Rotational Inertia times rotational velocity. Therefore, the momentum of a rotating object before is equal to the momentum of the rotating object after.
Next we learned about torque, or what causes the rotation of an object. Torque is determined by lever arm x force. Therefore, the larger the force or the lever arm, the more likely an object will spin.
Then we learned about Center of Mass, the average center position of the mass of an object, and Center of Gravity which is defined as the average position of weight within an object. In order for an object to be balanced its center of gravity must be within its basis of support or center of mass. Another way to increase stability is to lower your center of gravity or increase your basis of support. This is why wrestlers bend their knees and spread their legs when in a wrestling tournament.
Finally we learned about centripital force which is the center seeking force that pulls you into a circular rotation. When you are in a car and you make a sharp right turn, Centripital force is the only force acting upon you, your tendency to go in the opposite direction is not a force but inertia.
All in all, This unit required a lot of digesting, and some of the material had to resonate over a period of time before it sunk in (train wheels). I believe I should have asked more questions due to my problem was lack of understanding and lack of communication in this unit, but no worries. I think I grasped it in the end.
Physics in measurement
How do you find the mass of a meter stick, only using one 100g weight? The key is physics. Firstly you place your meter stick on a table surface, until the meterstick is completely balanced. Record where it meets the table. Do the same thing again, but apply the weight to the meterstick. Measure again where the meterstick meets the table. This will provide you with the lever arm. Since the meter stick is about 100cm long, you can assume the center of gravity is around the 50 cm mark. Next subtract the distance of the lever arm from the center of gravity to find the other meter stick's center of gravity. Finally, knowing the torque is always the same in the meter stick, you use the formula force times lever arm = force times lever arm to plug in your aquired results. Then you use algebra to solve for the mass of the meterstick!
Sunday, January 20, 2013
Wednesday, January 16, 2013
Experiment to demonstrate conservation of angular momentum
This shows how weight distribution manipulates the conservation of angular momentum.
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