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Chapter 9:1 What is Energy? Energy the ability to do work S.I. Unit: joules (J) Work- involves a transfer of energy and occurs when a force causes an object to move in the direction of the force (work = force x distance) S.I. Unit: joules (J) When work is done, energy is transformed from one type of energy into another type. Kinetic Energy- energy of motion All moving objects have kinetic energy Kinetic energy depends on speed (velocity) and mass Calculating the Kinetic Energy of Objects K.E. = m v2 2 K.E. = kinetic energy m = mass v = velocity faster objects – more kinetic energy objects with more mass – more kinetic energy Example problems: What is the kinetic energy of a turtle with a mass of 0.9 kg moving at 0.05 m/s? What is the kinetic energy of a 6,400 kg tractor trailer traveling at 25 m/s? Potential Energy- energy an object has because of its position or shape. Example: stretching a rubber band changes its shape. This gives it elastic potential energy. Gravitational potential energy- energy an object has due to its position above the Earth’s surface. Example: Depends object lifting up the rubber band gives it G.P.E. on the height and the weight of an G.P.E. = weight x height (w x h) = mass x gravity x height (mgh) Calculate the gravitational potential energy (G.P.E.) gained by a child with a mass of 40 kg when climbing up a 3 m height of stairs. Mechanical Energy- the total energy of motion and position of an object. M.E. = P.E. + K.E M.E. = mechanical energy P.E. = potential energy K.E. = kinetic energy Mechanical Energy can be all potential energy, all kinetic energy or part potential and part kinetic energy. Forms of Energy: Objects move because of energy. Energy is the ability to make things move. Energy is not like matter. Matter has mass and takes up space. Energy has NO mass and does NOT take up any space. There are 6 Forms of Energy: Chemical Energy- It holds the atoms in molecules together. It can be released by chemical reactions like burning wood. Electrical Energy- The movement of electrons through matter. Electricity is a form of electrical energy. Heat Energy- The vibration of particles within matter. The faster the particles vibrate, the more heat energy they have. Light Energy- The energy carried by light. Nuclear Energy- Holds protons and neutrons together in the nucleus of the atoms. This energy powers the Sun and nuclear power plants. Sound Energy- The vibration of air molecules. The vibrating molecules move tiny bones in your ears. The message of sound then moves to the brain. This is how you hear. Sound energy vibrates all forms of matter. Energy can be changed, or converted from one form to another. For example, the chemical energy in gasoline is changed into heat energy in the engine of a car. This heat energy is then converted into mechanical energy to move the car. Examples of Forms of Energy Electrical Chemical Light Sound Nuclear Heat Review: Complete on a separate sheet of paper. True or False Energy makes thing move. _____ Only moving objects have energy. _____ There is only one form of energy. _____ Everything has the same amount of energy. _____ Living things need energy. _____ Air molecules can vibrate. _____ Electrical energy powers the Sun. _____ Nuclear energy powers the Sun. _____ Energy takes up space and has mass. _____ Matter and energy are the same. _____ Open-Ended Response There is a limited amount of energy available on Earth. Why is it important that people conserve energy? Chapter 9:2 Energy Conversion Energy Conversion Changing from one form of energy to another. Energy is never lost, created nor destroyed, it converts into another form. The amount of energy you start out with is the amount of energy that you end up with. Only the forms of energy change. Ex. You flip on a light switch in your home and the lights go on. Electrical energy has changed to light energy. Thermal Energy Thermal energy is always in energy conversion because some of the original energy converts into friction which is useless thermal energy. Energy Conversion of a Trampoline A change from one form of energy into another. An energy conversion example involving Kinetic and Potential energy is a trampoline. When you’re on a trampoline and you jump down, your kinetic energy is converted into potential energy of the trampoline. Then the trampoline’s potential energy is converted to kinetic energy, making you bounce up. At the top of the jump, all of that energy is turned back to potential energy. Then right before you hit the trampoline, all of the potential energy is converted back to kinetic energy. Review: Complete on a separate sheet of paper. ( same as before) True or False Heat is a form of energy. _____ Heat is the only form of energy. _____ Heat energy is sometimes useful. _____ Energy can change from one form to another. _____ Energy conversions always give off heat. _____ Heat energy can change to mechanical energy. _____ Mechanical energy can change to heat energy. _____ Energy changes are called conservations. _____ Energy changes are called conversions. _____ Open-Ended Response List the three parts of the “Law of Conservation of Energy”. Start each part with the word “Energy”. Chapter 9:3 Law of Conservation of Energy Law of Conservation of Energy Energy is like matter, it cant be created or destroyed. Energy is transferred in an energy conversion. Explain the energy conversions occurring within this closed-system. Chapter 9:4 Energy Resources Energy Resources A natural resource that can be converted by humans into other forms of energy in order to do useful work. Renewable Resource- Can be used and replaced in nature over a relatively short period of time. (some are practically limitless) Solar (Sun), Water (Hydroelectric), Wind (Turbine), Geothermal (Geysers) and Biomass (Burned Organic Matter) Nonrenewable Resources Cannot be replaced after they are used or can be replaced only over thousands or millions of years. Fossil Fuel: The most important and common resource. They are formed from the buried remains of plants and animals that lived millions of years ago. These plants stored energy from the Sun by plants. Forms of Fossil Fuels: Coal, petroleum, and natural gas Nuclear Energy: Nuclear energy is energy that is released either by splitting atomic nuclei or by forcing the nuclei of atoms together. Remember: The Sun is the source of most energy on Earth. Depending on where you live and what you need energy for, one energy source can be a better choice than another. Energy Resource Activity Select 3 Nonrenewable and 3 Renewable resource. Write the advantages and disadvantages of each resource. Use page 237 for help. Open-Ended Response Think about how life will change when fossil fuels run out. How will the environment, jobs, travel, sports, and industry be affected? Write or illustrate a short story that describes a day in such a time.
