Brief OverviewTo begin this unit, we defined energy as the thing needed for an object to do something. As we progressed, we learned more rules about energy, like how it cannot be created or destroyed, but rather is stored in different forms. We observed the different forms that energy can be found in, such as kinetic energy, gravitational potential energy, elastic energy, thermal energy, and chemical energy. We focused on the relationship between them, and how energy could transfer from one to another. We also learned about how energy could be gained or lost through working, heating, or radiating. We then focused on finding the energy of systems based on their position and motion. Lastly, we focused on energy’s relation to power, and the release of it.
|
Representing Energy Transfers with Bar (LOL) ChartsUsing Bar LOL Charts, we can effectively represent energy transfers through the different types of energy in the system. We start by plotting the initial energy in the system, using relativity for the amount of bars. It represents the different types of energy in the system. In the middle is a circle representing the system of the energy, and where it is flowing. There is often an arrow going in or out of the system, which represents energy either entering or leaving the system through a working, heating, or radiating relationship. On the right, we have our final graph, which shows the energy in the system after the event has occurred. Through this and the arrow, we need to show that the energy is neither created nor destroyed, simply transferred to a different form, or is leaving or entering the system.
|
Energy Problem SolvingThroughout the unit, we learned many different equations to calculate the different types of energy. Specifically, we learned the equations for gravitational potential energy, kinetic energy, and elastic potential energy. Because of the law of conservation of energy, we are often able to manipulate these equations and set them equal to each other so that we can solve for different values of energy and specific variables within the equation.
|
WorkThe work on a system is an expression of the transfer of energy through an external force acting on the system. Similarly to heating and radiating, it represents a force acting on the system, where energy either enters or leaves the system. The value of work depends on the force acting upon the system, and must still hold true to our law of conservation of energy. It also can change based on the displacement of the object in the system. The larger the displacement, the larger the value of the work. To solve for the value of work, we use the equation: W = (Force)(Displacement). Work can be either positive or negative. Work is positive when the work puts energy into the system. Work is negative when the work takes energy out of the system. Work is very useful in helping to maintain our law of conservation of energy, as we can add or subtract it to make this law hold true, as energy cannot be created nor destroyed.
|
PowerThe power of a system is an expression of how quickly a system can release energy. We can label it as the rate of transfer of energy for a system. When a system is more powerful, it releases more energy at a quicker rate. When a system is less powerful, it releases less energy at a slower rate. To represent power, we use the equation P = (Work)/(Change in time). Because work is the change in energy, we divide it by the change in time to calculate the rate of the transfer of energy for a system.
|
Relating Energy/Work/Power to Forces and MotionTo determine the energy and work of the system, force and motion are crucial tools to help us calculate those values. When an external force is acting upon the system, it is represented as work on the system, and we can use our force equations to calculate that working force that is either putting in or taking out energy from the system. For kinetic energy, we need to calculate the velocity of the object to solve the equation. To calculate the velocity, we need to look at the motion of the object. If the object is moving faster, the velocity will be higher, meaning the kinetic energy will be larger. Next, when we determine the gravitational energy, we need to use the gravitational constant for acceleration. To do this, we need to look at the motion of the object to calculate the value of the energy. Finally, for elastic potential energy, we need to calculate the displacement of the spring. To do this, we again need to look at the motion of the object and the position of the spring. To calculate these different forms of energy, we need either a force or motion to determine their values.
|
Connecting Representations of Motion with Representations of Forces with Representations of EnergyMotion, force, and energy are all interconnected because changing one almost always means that one of the others will change. We can express all three of these over time, through different graphs. Motion graphs are usually represented by a position time graph, showing the object’s motion over time. Force graphs are usually represented by system schemas and force models, helping us visualize the direction and the magnitude of forces that are in the system. Energy graphs are usually depicted as the change in energy over the period of time, showing how different forms of energy change over time, while holding true to the law of conservation of energy.
|