Student Reader. Energy Systems UNIT 7. E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

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1 Student Reader UNIT 7 Energy Systems E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

2 Front Cover: The cover shows a photograph of a sled that is not in motion. The movement of a sled from one place to another is an example of a mechanical energy system. A push or the pull of gravity inputs energy into the sled. The movement of the sled is the output energy. The sled stops moving due to friction between the bottom of the sled and the ground. E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

3 Table of Contents Unit 7: Energy Systems Section 1: Forces 4 What Powers a Sled? 4 Where Does Energy Come From? 6 In the Know: Forms of Energy 7 What Is Friction? 8 Section 1: Try This on Your Own 9 Section 2: Electromagnetic Motor 10 Where Are Energy Systems Found? 10 How Do Magnets Work? 11 What Is a Motor? 12 Electromagnetic Motor Activity Sheet 13 Section 2: Try This on Your Own 14 Glossary 15 E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

4 1 Forces Main Ideas Energy is a force that is able to do work. There are several forms of energy. Energy is never created or destroyed; it constantly changes forms as it moves through energy systems. Friction is the transfer of mechanical energy to heat energy that takes place when two moving objects or substances rub against each other. What Powers a Sled? As a boy, Lance Mackey dreamed of winning the Iditarod Trail Sled Dog Race. It s not an easy task. The roughly 1,900 kilometer race across the Alaskan wilderness can take 8 to 20 days. Racers may face blizzards and sub-zero temperatures. Lance watched his father and older brother both win, and it was his turn to carry on the family legacy. Lance overcame many hardships to train for the race, but that didn t stop him from winning first place in 2007, 2008, 2009, and E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

5 Lance s victories weren t just chance. It takes strategy to win a sled race. A dog sled racer must know about forces before he or she can race. An Iditarod race allows each musher (racer) to train a team of 12 to 16 dogs. Lance needed to train his dogs until they were strong enough to cross many kilometers of icy roads. He also needed to use a sled that was light enough for his dogs to pull. Racers usually train dogs called huskies. The Iditarod can last many days, so it is important that the racer and his dogs take breaks. Dogs need energy to pull the sled for such a long distance. They need to be fed at least 10,000 calories a day, with a diet that may include lamb, chicken, beef, moose, or salmon. The dogs need all this energy because it takes a great amount of force to pull a grown adult like Lance, as well as his supplies, especially at a speed fast enough to win a race. force the energy (or effort) needed to do work energy a force that is able to do work (e.g., move an object, heat up an object, charge an object) Mushers know that the more mass something has, the more force is needed to move an object across any distance. The Iditarod has rules about how many dogs can pull a racer to make the race fair. A team of 30 sled dogs would be able to move much faster than a team of 6 sled dogs. E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

6 energy system a set of connected parts that transfers an input of energy to a different output of energy conservation of energy a physical law that states that energy cannot be created or destroyed; it can only be transferred from one form to another Where Does Energy Come From? Dogs can pull sleds because their bodies, like all animals, transfer the chemical energy in food into mechanical energy to move. A dog is an example of an energy system because there is an energy input (food) and an energy output (movement). According to the law of conservation of energy, energy cannot be created or destroyed; it can only be transferred from one form to another. Energy is always either being stored or doing work. Potential energy is energy that is being stored. A stretched archer s bow is an example of potential energy. The more the archer pulls back the bow, the farther the arrow will travel. Another example is a bicycle at the top of a hill. The higher the rider is on the hill, the farther the bicycle will travel once it goes over the hill. The energy of a moving arrow or bicycle is called kinetic energy. Kinetic energy is energy in motion. The more kinetic energy something has, the more work it can do. energy in kinetic energy potential energy energy out kinetic energy E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

7 In the Know: Forms of Energy Forms of Potential Energy chemical: energy stored in the bonds of atoms and molecules (e.g., food, wood, gasoline) gravitational: stored energy related to an object s height above the ground (e.g., a roller coaster at the top of the track) nuclear: energy stored in the nucleus of an atom (e.g., energy that holds the nucleus together) elastic: energy stored in objects when stretched (e.g., compressed springs, stretched rubber bands) static electricity: energy stored in an electric charge (e.g., static charged balloons) Forms of Kinetic Energy heat: the motion of atoms and molecules in a substance or object as its temperature increases (e.g., boiling water) sound: energy produced by sound vibrations moving through a substance in waves (e.g., music, talking) light: the movement of energy in a wavelike pattern that comes from light (e.g., visible light, X-rays) mechanical: the energy of a substance or system due to its motion (e.g., car moving, windmill blades turning) current electricity: the movement of charged particles through a conductor (e.g., electricity, lightning) E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

8 What Is Friction? friction the transfer of mechanical energy to heat energy that takes place when two moving objects or substances rub against each other Sled dogs also need energy to overcome friction. Dogs may slow down as they run because their feet rub against the ground each time they take a step. The rubbing causes the mechanical energy of the dog s movement to be transferred into heat energy where the dog s foot and the snow meet. Sledracing dogs must wear boots because friction can cause blisters and cuts on the dogs feet. Friction is everywhere because surfaces are never perfectly smooth. For example, if you were to look at a tabletop under a microscope, you d see that there are tiny bumps and ruts. These bumps scrape against objects moving across the table the same way snow scrapes against a dog s foot. Smooth surfaces need less force to move an object because less energy is lost to friction. Rough surfaces require more force to move an object because more energy is lost to friction. E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

9 Section 1: Try This On Your Own Classify: Review the different forms of energy. Create a chart with two columns: one for potential energy and one for kinetic energy. Draw as many examples of potential and kinetic energy as you can find in each of the columns. Research: Learn more about the Iditarod race. Visit the student section under the resources section of Iditarod.com. Learn more about the racing dogs and watch the video about how veterinarians take care of the dogs. Write: Keep a record of where you get energy from and how you transfer it to other places. For example, the food you eat gives you the energy to move. Next, record how your mechanical energy moves other objects. Experiment: Find out which pair of your shoes has the most friction. Tape a rubber band to the back of the shoe. Place the shoe on a flat surface and pull on the rubber band until the shoe starts to move backward. Measure the maximum length of the rubber band as it moved the shoe. Repeat with different types of shoes. The shoes with the most friction require the most force to move. E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

10 2 Electromagnetic Motor Main Ideas Magnets are objects that attract or repel other magnets, as well as iron and steel metals. An electromagnet is a tightly wound coil of wire that becomes a magnet when electricity passes through it. A motor is an energy system that transfers an input of electrical energy into an output of mechanical energy. Where Are Energy Systems Found? Household electronics are all examples of energy systems. In a toaster, an input of electrical energy produces an output of heat energy to toast your bread. electromagnet a tightly wound coil of wire that produces a magnetic field when electricity passes through the wire Several energy systems can be present in a single device. For example, the handle of a toaster is held down by an electromagnet, transferring mechanical energy into elastic energy in the loaded springs. As soon as the toaster has reached the pre-set temperature, the electromagnet becomes demagnetized and releases the toaster handle and spring, allowing the bread to pop out. E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

11 How Do Magnets Work? Magnets are used in many household devices (e.g., doorbells, speakers, and television sets), because they can attract or repel other objects without touching. Iron and steel metals can be moved by magnets. Magnets also move other magnets. A spinning magnet can even push electricity through a circuit without a battery. The rules of magnetism state that opposite poles attract and like poles repel. This means that the north pole of one magnet always attracts the south pole of another, but two north poles repel each other and two south poles repel each other. Magnets are categorized by their magnetic fields: Natural magnets are magnetized rocks. Permanent magnets are magnetized for a long time. Temporary magnets are magnetized for a short time. Electromagnets are tightly wound coils of wire that produce a magnetic field when electricity passes through the wire. permanent magnet an object that stays magnetized for a long time without electricity E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

12 What Is a Motor? motor a machine that transfers an input energy into mechanical energy output Magnets are part of many electronic devices because they are used to drive small motors. A motor is a machine that transfers an input energy into mechanical energy output. For example, car wheels turn because a car s motor transfers chemical energy (electrical, gasoline, or diesel) into mechanical energy. In an electromagnetic motor, electrical energy is transferred into mechanical energy. The electromagnetic motor has two parts: an outside permanent magnet and an inside electromagnet. The electromagnet becomes magnetized when connected to an electrical current and then spins rapidly because it is surrounded by the permanent magnet. If a gear is attached to the spinning electromagnet, the gear can be made to do work. E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

13 Name: Class: Date: Electromagnetic Motor Activity 1. Diagram the electromagnetic motor system. Label each material and use arrows and labels to show how energy is transferred through the system. E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

14 Section 2: Try This on Your Own Diagram: Find examples of energy systems in your daily life. Diagram the energy input and energy output of each system. For example: the electrical energy of a wire is transferred into heat and light energy by a light bulb; the chemical energy of the food you eat is transferred into mechanical energy by your muscles. Observe: Place a AAA battery, and then a 9-volt battery in the electromagnetic motor circuit to see how the different batteries affect how fast the motor spins. Based on what you know about force and energy, what would it mean about the battery if it makes the motor spin faster or slower? Research: Learn about how a device that uses an electromagnet works. Choose a doorbell, toaster, or television set. Look at diagrams of your device in a book or online. How does the electromagnet do work in the device? Hypothesize: Cranes in junkyards use magnets to transfer cars and other large objects from one place to another. How do you make an electromagnet stronger? E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

15 Glossary 1. conservation of energy a physical law that states that energy cannot be created or destroyed; it can only be transferred from one form to another 2. electromagnet a tightly wound coil of wire that produces a magnetic field when electricity passes through the wire 3. energy a force that is able to do work (e.g., move an object, heat up an object, charge an object) 4. energy system a set of connected parts that transfers an input of energy to a different output of energy 5. force the energy (or effort) needed to do work 6. friction the transfer of mechanical energy to heat energy that takes place when two moving objects or substances rub against each other 7. motor a machine that transfers an input energy into mechanical energy output 8. permanent magnet an object that stays magnetized for a long time without electricity E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM

16 E5 Student Reader v. 8.0 Unit 7 Page KnowAtom TM