PHYSICAL SCIENCE : ELECTRICITY : 02.01 ENERGY What is Energy? Has anyone ever told you to eat something because you need the energy? Have you ever seen a commercial advertising an energy drink or energy efcient appliances? Energy is something that everyone uses, so what is it? Notice, the energy described in these situations involves some sort of motion. When you learned about motion, you also learned about doing m. Energy is the ability to do work. It comes in various forms and transfers from one object to another as forces are applied. Energy is measured in the SI unit Joules, similar to work. The following units represent a joule. Energy is fundamental to movement, chemical reactions, electricity, and all the other topics we will be studying in this course. Energy is the ability to change or move matter. Energy exists in many different forms. Think about how you use energy in your own life. o You get chemical energy from food to help your body move. o Energy from sunlight is used by plants so they can grow and make food. o Power plants provide energy in the form of electricity to cities and towns. o Energy in gasoline gets your car's engine moving so you Show Text Version can drive down the street. All forms of energy can be classied into two categories. potential energy and kinetic energy. Let's take a look at these two types of energy. Kinetic Energy Kinetic energy is energy that an object has while in motion. These are all examples of kinetic energy: a A car rolling down the street. a Particles of air moving around inside a hot air balloon. o A baseball being thrown across the eld. AP Images 2009 I Energy Conversions As you have seen, there are many different forms of energy and they can each be categorized as either potential or kinetic energy. Where does that energy come from? Energy can be converted from one form to another, but it is not created or destroyed in ordinary physical and chemical processes. This statement summarizes the Law of Conservation of Energy. The law of conservation of energy tells us that all of the energy available at the start of a conversion or transfer still exists in some form of energy after the change is complete. Let's take a look at some additional examples. Explore the sections below to deepen your understanding of energy conversions. Radiant to Chemical Energy Nuclear energy stored in atoms inside the sun is converted to radiant solar energy that travels to the Photosynthesis Earth. That radiant energy in sunlight is converted to h ' | ' | t b ll d c emlca energy In pan s y a process ca 9 Oxygen is photosynthesis. :. J" , Released People and animals eat fruits and vegetables to get the stored chemical energy from plants and convert that to other forms of energy as they go throughout their day. Energy Conversions in Action Now let's look at an example on a roller coaster. Electrical energy from a motor is converted to mechanical energy as the chain pulls a roller coaster up the rst big hill. The higher up the hill the roller coaster is pulled, the greater its gravitational potential energy. As it travels down the hill, that potential energy is converted to mechanical kinetic energy. As the roller coaster travels across the track, some of the kinetic energy is converted to heat because of the friction between the coaster and the track. Now let's think of a roller coaster in action and visualize the conversions between potential and kinetic energy. If a rollercoaster is riding over hills, what are the levels of potential and kinetic energy? Energy Models So far. we have discussed the different forms of energy, how one can transfer into another, and how the quantity of energy is conserved. In science. it is important to identify the system being investigated. so we can predict and monitor how energy (and matter} will move. Systems A system is the container or objects of interest in a particular investigation. A system could be an atom. chemical reaction. cell. person. community, ecosystem, planet, solar system, or universe. Systems allow scientists to recognize all the parts or pieces interacting together at any given time. They also establish what is not interacting. Everything else that is not part of the system being examined is referred to as the surroundings. There are three types of systems open, closed and isolated. Each are ' _ rain _ i_ mass;- classied by how they transfer energy and matter. - heat from Sun .1 {energy} Consider one example of a system: the ocean. It takes in energy from an ' latent heat outside source. the sun. in the form of heat. This heat causes some water (energy!) to evaporate from the ocean. and the evaporation of water transfers latent __ . . a: _.. :_H __ heat energy back to the atmosphere. The evaporated water transfers mass ' 12.0%Hg8lmages from the ocean to the atmosphere. but mass is added to the ocean through the water cycle. Let's explore the three types of systems in more detail. After you do, can you identify what type of system the ocean is? Isolated System In an isolated system. neither matter nor energy is permitted to exchange 1* with the surroundings. This means that the total amount of energy and Isma'wfmm matter contained in an isolated system will remain constant. because energy and matter cannot enter or leave. . EICl'Ii nga or energy .Emangw mam Our universe is an example of an isolated system. Scientists believe that ISOLATED the total amount of matter and energy remain constant within the universe and cannot be exchanged with any surroundings. There are few examples of true isolated systems. and they are very rare in nature. This is because it can be difcult to completely block the exchange of energy between a system and its surroundings. Some systems come closer than others. Using insulated containers, such as coolers and foam cups. helps to minimize the amount of heat ow between the system and its surroundings. but they are not truly an isolated system. Closed System In a closed system. energy can enter or leave the system but matter cannot. I Closed System The planet Earth is an example of a closed system. The outer edge of the -. iv J atmosphere acts as a boundary between the system. Earth. and its .E'chinmmw surroundings. Matter does not enter or leave the system. except for the .Exchangeal mm occasional meteorite or shuttle. but energy is freely transferred between the CLOSED Earth and its surroundings. Energy in the form of radiation from the Sun passes through the atmosphere to the Earth's surface. The Earth also emits radiation back out to space. Because energy passes across its atmosphere but matter usually does not. the Earth is considered a closed system. Open System In an open system. both matter and energy (often in the form of heat} are Energy conversions are going on all around you. Some of them are very exciting and obvious, like the roller coaster. Others go on without you even knowing, like the plants using energy from the sun and converting it into food. Both of these are great examples of the law of conservation of energy. When you reach this point, you will be able to: o differentiate among the various forms of energy 0 recognize that energy can be transformed from one form to others 0 use a model to calculate the change in energy in a system 0 compare and contrast open, closed, and isolated systems Energy Transformations Rube Goldberg Device Have you ever wanted to be an inventor? Now is your chance! You will test and redesign a Rube Goldberg device, then build one of your own. Rube Goldberg devices use simple everyday items and take advantage of simple potential-to-kinetic energy conversions. When several of these conversions are combined, the device is able to perform a simple task. Like all designs, this project will have some constraints. A constraint is a limitation or condition that must be satised by a design so that it can function properly. For example, you may only be able to use certain materials, or you might want the device to operate at a certain speed. Start by downloading the Energy Lab Worksheet and review the grading rubric. Then follow the steps below to complete Parts 1 4 of your lab worksheet. 1. Use the virtual Rube Goldberg Machine interactive to complete Part 1. Make sure to pay attention to the energy conversions that happen! Think about how this machine demonstrates the law of conservation of energy. 0 Read the introduction, then select Begin. 0 Fix the device so the ow of energy is not interrupted, and the window shade can be closed. Rube Goldberg Activity You have learned that energy is neither created nor destroyed: it is transferred from one object to another. Your goal in the lab activity is to make the necessary adjustments so the Rube Goldberg device will function properly. This machine is designed to pull down the window shade. Can you make the necessary adjustments to the objects within the device to get the window shade down? As you make these adjustments, notice the path of energy transfer throughout the device. Rube Goldberg devices are great examples of energy conversions; let's get started! A series of everyday objects are arranged so that the movement of one object will cause the next object to move until a window shade is pulled closed. Some of the objects need to be moved or set up so that the series of movements will result in the shade being pulled down. A ball is knocked off of a shelf to a ramp, where it rolls into a tube that guides the ball down to a pulley system. When the pulley system is moved by the weight of the ball, the other end of the system pushes a pair of scissors closed. When the scissors close, they cut a string that is holding up a 5- pound weight. When the string is cut, the weight falls onto a catapult that has a small ball at the other end. The force of the falling weight propels the small ball up into the air, where a sling shot is pulled back and ready to be shot. The ball releases the sling shot, which shoots a ball across the room where it knocks down a series of books. The series of books fall over like dominoes, and the last one falls off of the shelf and into a bucket. The bucket is hanging from a string that is connected to the window shade, so when the book falls into the bucket, the bucket falls down to the ground and the string pulls down the window shade. .l. n_:._