As I have learned during our unit of the Conservation of Energy, energy is never created or destroyed; it does not have forms or types but is a universal substance-like quantity that is capable of creating change. Energy is stored in many forms where it can be easily retrieved such as elastic (Eel; energy stored in rubber bands, springs, etc.), kinetic (Ek; energy due to motion), gravitational potential (Eg; energy due to an object’s height on earth or position in a gravitational field), and chemical potential (Echem). In addition, energy can be stored in more abstract forms where it is hard to retrieve such as thermal energy (Ethermal; energy due to the random motion of molecules; heat) and sonic energy (Esonic; energy due to the wave motion of molecules; i.e. sound). These two energies are often classified into the category of dissipated energy (Ediss), or in many situations internal energy (Eint), the energy that is dissipated due to friction in a particular system. In our physical system, energy is transferred in three manners: Heating (the transfer of energy in a system from the warmer object to the cooler object; temperature is a quantitative measure of the average kinetic energy of molecules), Electromagnetic Radiation (visible light, microwaves, ultraviolet light, and infrared light), and Working (the transfer of energy due to forces that cause displacements). In this unit, we mainly focused on energy transfer through “work” as is the case when energy is transferred into a system via an external force. I have learned how to create energy flow diagrams, bar graphs that qualitatively analyze the transfer and conservation of energy, and some equations that relate work done with a force applied (W = F*x; this equation is only true when the directions of F and x are parallel). Also, I learned that power is a rate of work, the work-energy theorem (W=deltaKE=deltaPE), and that the mechanical energy of an object equals the sum of its potential and kinetic energy.
During this unit I was frequently confused due to large amount of information that was presented at one time and therefore, need to continue to study the main concepts behind energy problems and the best way to solve them. Due to the large amount of equations, variables, and possibilities to solve problems, it was at times difficult to know the best way, or even a way, to solve a problem. However, I realized that by sketching the situation or drawing an FBD I could clarify some of the intricacies of the problems and solve them easier.
My problem solving skills during this unit have improved greatly. The most important realization for me was that when working with many energy related problems, a good way to start is to set the sum of the storage forms of energy at the initial instance equal to the sum of the storage forms of energy at the final instance of the situation. In addition, the problem solving strategy in the book on how to best analyze a problem (such as asking if the object is at a height, moving, is in contact with a spring, or if there is a force applied through a distance) really helped in the solving process. In my opinion, my biggest weakness is being able to work quickly through problems and make fast connections. I try to put my best effort into every problem that I attempt and believe that my understanding of energy has risen greatly. With every problem that I try, I think that I have a greater grasp of the subject. I hope that as the year goes on, I can continue to increase my knowledge and understanding of the physical world around me and be able to analyze situations thoroughly.
When analyzing everyday life, many examples of energy and energy transfer can be easily seen. From when you wake up to when you go to bed, energy is constantly performing work and being converted and conserved. When you eat breakfast in the morning, you provide nutrients to you cells that convert them into energy that your body can use so that you can perform activities throughout the day. Driving in the car to school or work, your car is converting chemical energy from fuel and air into kinetic energy to make the car move, creating dissipated energy (heat) in the process. As I climb the stairs to get to my classes, I perform work on myself and gain gravitational potential energy and lose some of the energy from food in the process. Take for example, a simple machine that is very common in everyday life: the inclined plane. This machine helps people by making it easier for people to move objects to a new height, i.e. movers trying to get heavy boxes into a truck whose cab is meters off of the ground. This can all be explained due to energy and work done. In a perfect world with no friction, because the object will end at the same height with the same potential energy, it does not matter if the object will be lifted one meter, or rolled/pushed up an incline plane 4 meters long. As can be seen with the equation W=F*x, because the amount of work in these two situations are the same, the amount of force needed to move the object up the ramp is less that picking it straight up because you are moving it a longer distance. Even though we do not live in a frictionless world, this is even true to a certain extent like when using dollies or carts. Many thrilling rides such as a riding on a rollercoaster or bungee jumping can be easily explained through energy. In addition, even elevators, Newton’s Cradle, and the motion of planes and rockets can be analyzed and explained by looking at their energies. Energy has always been, is now, and will always be the same. There is the same amount in our universe as there was yesterday, and there will be tomorrow, no more, no less. For this reason, at least for me, that is why energy is the fuel of our universe.
Work/Energy: 1 joule (J)=1 Nm
Power: 1 watt (W)=1 J/s
Spring Constant: N/m