Energy and It’s Forms

1. Energy and It’s Forms Energy Chapter 15 Section 1 Physical Science

2. Energy and Work • Energy is known by the changes it causes ex: sound or motion (hear an avalanche and see the snow) • Work is a force acting through a distance • Energy is the ability to do work; energy is transferred by a force moving an object through a distance

3. Energy and Work • When work is done on an object, energy is transferred to that object • Work is a transfer of energy • Both work and energy are measured in joules TASK: carry backpack up the stairs Do work on the backpack by lifting in against the force of gravity. You get the energy from your muscles, your muscles get the energy from food. The food gets its energy from plants (or animals that eat plants) that get their energy from the sun

4. Kinetic Energy • There are MANY forms of energy, but it can be classified into 2 types : kinetic and potential • Kinetic Energy is the energy of motion Greek “kinetos” means moving Kinetic Energy (KE) = ½ mv2 units are joules kilograms m/s

5. Potential Energy • Potential energy is energy that is stored as a result to position or shape. It is energy with the potential to do work Ex: when playing a guitar, you pull the strings back in order to create music. The energy is stored in the stretched string and it gains potential energy. When you let the string go, the potential energy (stored energy) is converted into kinetic energy (energy of motion) EX: you can also store energy when you lift a book and hold it in the air. Let go of the book and the potential energy (stored energy) is turned into kinetic energy (energy of motion) as the book falls to the floor

6. Potential Energy • Two types of potential energy: gravitational and elastic • Gravitational Potential Energy is potential energy that depends on an objects height Increases when an object is raised to a higher level Ex: person sitting in a dunk tank has GPE. When the seat is let go GPE is converted into KE, work is done as the person falls in the water Depends on mass, height and gravity Gravitational Potential Energy (GPE) = mgh units are joules Mass kg Height m Accel. Gravity 9.8 m/s2

7. Elastic Potential Energy • The potential energy of an object that is stretched or compressed is elastic potential energy • Something is considered elastic if it springs back to original shape after being stretched or compressed Ex: stretch a rubber band, you do work on the rubber band and the energy is stored as elastic potential energy

8. Example Energy Problems • A .1 kg bird is flying at a constant speed of 8.0 m/s. What is the birds kinetic energy? KE = ½ (.1 kg) (8 m/s)2 KE = 3.2 J • A diver at the top of a 10 m high diving platform has a mass of 50 kg. Calculate the potential energy of the diver. PE = (50 kg) (9.8 m/s2) (10 m) PE = 4900 J

9. Forms of Energy: Mechanical • Mechanical Energy is the energy associated with the motion and position of everyday objects Applies to more than just machines • The sum of an objects potential and kinetic energy • Created from chemical energy EX: speeding train (kinetic), sprinting athlete (kinetic), bouncing ball (kinetic and potential), pulling back a arrow (potential), holding a barbell above your head (potential)

10. Forms of Energy: Thermal • Everything is made of matter and matter is made of particles. • The particles are always randomly moving and thus have kinetic energy • Thermal Energy is the total kinetic energy of the microscopic particles in an object. Related to temp and heat • The faster an objects atoms move, the more its thermal energy increases and the object becomes warmer. When hot, the object may emit light EX: boiling water; thermal energy or heat is applied to the bottom of the pot. The energy is transferred to the water. The particles in the water begin moving faster and the water will turn to steam

11. Forms of Energy: Chemical • Chemical Energy is the energy stored in chemical bonds • When the bonds are broken, the released energy can do work • All chemical compounds store energy, including coal and gasoline EX: cars use the chemical energy stored in gas to move. Some of the chemical energy is converted into mechanical energy to move the car EX: a fire is fueled from the chemical energy stored in wood. Some of the chemical energy is converted to thermal energy and produces heat and light

12. Forms of Energy: Electrical • Electrical Energy is the energy associated with electrical charges that exert energy to do work • Many devices use electricity, or electrical energy EX: batteries convert chemical energy into electrical energy to operate flashlights, CD players, cell phones and radios

13. Forms of Energy: Electromagnetic • The sun radiates electromagnetic energy into space and it the source (directly or indirectly) of most of the worlds energy supply • Electromagnetic Energy is a form of energy that travels through space in the form of waves • Waves can travel long distances through air and space EX: visible light and x-rays EX: plants use the electromagnetic solar energy and convert it to chemical energy through a process called photosynthesis

14. Forms of Energy: Nuclear • The nucleus of an atom is held together by strong and weak nuclear force, which can store a lot of potential energy • The energy stored in the atomic nucleus is called nuclear energy EX: A nuclear power plant uses nuclear fission reactions to generate electricity. Nuclear fission releases energy from splitting nuclei apart EX: Nuclear Fusion releases energy from combining less massive nuclei to form more massive nuclei. The heat and light of the sun is produced from the fusion of hydrogen nuclei into helium nuclei

15. Energy Can Change Forms • Energy forms can be converted from one form to another • Light bulb uses electrical energy (produces light), some of that energy is converted to thermal energy (produces heat) • Energy can be transformed; IT CANNOT BE CREATED OR DESTROYED!!!