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.