Saturday, February 20, 2010

Reflection: conservation of energy

Part A:

This unit we learned about the conservation of energy. We learned that energy is a conserved substance like quantity with the ability to produce change. I also learned that energy can be moved around and stored in different ways but energy itself is unchanged. Energy does not exist in different forms, it is just stored in different ways. While there are not different types of energy, energy is distinguished by the mechanism that is used to store it, such as kinetic, elastic, gravitational potential, and chemical potential. Each of these is not a different type of energy, just a different method for storing energy. As energy is transferred from one method of storage to another, the total amount of energy remains unchanged (this is conservation of energy). energy can be transferred in or out of a physical system in there ways, working (energy is transferred by forces that cause displacements), heating (temperature differences between a system and its surroundings cause energy to be transferred from the warmer object to the cooler object), and radiation (matter loses energy as it emits electromagnetic radiation and gains energy as it absorbs it). I also learned how to represent the transfer of energy with an energy conservation bar diagram. We used bar graphs to represent the initial and final energies and an energy flow diagram to represent what happens during the process of transferring energy. I also learned about work, which is the amount of change that a force produces when it acts on a body. Work is a scalar quantity and its unit is the joule. The rate at which work is done by a force is called power and the unit of power is watts. Power is also equal to the force multiplied by the velocity. After learning the amount of change that a force produces and the rate of that change, I learned about some different transfer methods of energy, namely kinetic energy, potential energy, and elastic potential energy. Kinetic energy is the energy a body has by virtue of motion and is calculated by dividing the product of the mass and the square of the velocity by 2. The gravitational potential energy of a body is found by the product of the mass of the body, the acceleration due to gravity, and its height above a given reference level. elastic potential energy is potential energy associated with elastic materials and is found with the equation PEe=1/2 k(x*x) in which k is the spring constant and x is the displacement. All these transfer methods of energy can be related with work using the work energy theorem. This Theorem states that the net work done on a body is equal to the change in energy of that body, which basically means that Work=change in KE=change in PE. I could then use all these equations to solve problems in which I was given portions of any equation, put them all together and come up with an answer.

The only thing I have found difficult in this unit was when we got into conservation of energy and had problems in which we were figuring out velocity and only being given mass force and displacement. It ocnfused me to come up with the equation for the of the final energy but once I did that I was able to solve the problem much more easily

I feel my problem solving skills have gotten better in this unit, just as they have in units past. The problems we get require us to use critical thinking bacuse not all of them can be approached the same way, and the more practice I have gotten at solving these problems the better my skills have become.

Part B:

The things we learned about conservation of energy are very relevant in real life situations. For example, te physics principles of the conservation of energy are clearly demonstrated in roller coasters. when you are at the top of a ridge in the roller coaster you have x amount of potential energy. When you go down, at the halfway point you have the same amount of energy but now half of it is kinetic and half potential. the instat before the tracks level out and you are almost at ground level, you still have the same amount of energy that you had at the top but now it is all kinetic energy as you are moving (except for a small amount that is internal energy due to friction). Roller coasters clearly show the law of the conservation of energy and demonstarte that energy is only stored in different ways, it does not change forms and is neither created nor destroyed.

Monday, February 1, 2010

physics and Recoil Voki

Get a Voki now!

Dyanmics Application: How is Newton's third law responsible for recoil?

this is a Glog I created to show how recoil is attributed to Newton's third law of Motion. The glog explains why there is recoil and it also talks about why bigger and more powerful guns have more recoil.

edited Dynamics application Glog