Sunday, February 21, 2010


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.

Physics Class Notes


  1. It looks good you have a spelling error on line 7. It says whe you probably meant the. Your connection to a roller coaster is good too.

  2. The objective of doing reflections is NOT to just re-word the class notes. I'll rather have you writing what YOU learned using your own words. Please re-write your reflection!

    Also, at the end you said that the car "gains internal energy"? how about the road?