Transcript Starter
Starter Directions: Copy the following examples. Answer using the following terms: Mechanical, Thermal, Chemical, Electrical 1. Hydroelectric dam 2. A horse pulling a cart 3. A thermos of hot coffee 4. The bonds holding atoms together in food Energy Conversion and Conservation Day 31 Review • Directions: Complete the statements below. 1. What is the formula for work? 2. What is the formula for power? 3. What is the work if a horse pulls a box 5m with a force of 10 N? 4. It takes 8 seconds for a pulley system to lift a load with 400 J. How much power is required? Energy Conversion • Energy can be converted from one form to another. • The process of changing energy from one form to another is energy conversion. Example • What energy conversions occur in lighting a match? • In lighting a match, your muscles use chemical energy moving your hand to strike the match against a rough area on the matchbox. Friction between the match and the matchbox converts some of the match’s kinetic energy into thermal energy. The thermal energy triggers a chemical reaction on the match tip, releasing some of the match’s stored chemical energy. The stored chemical energy is then converted into thermal energy and electromagnetic energy in the flame. Example • What energy conversion takes place when you turn on a battery powered radio? • Chemical energy in the battery is converted into electrical energy in the radio. This electrical energy is converted into sound, a form of mechanical energy, and a small amount of thermal energy. Energy Conversion (gravity) • The gravitational potential energy of an object is converted to kinetic energy of motion as the object falls. • A seagull has just caught his meal, an oyster, and is trying to get into the oyster’s shell. What do you think the sea gull is going to do to open the shell? • When is the oyster’s kinetic energy the greatest and when is the oyster’s potential energy the greatest? • Potential energy is greatest at maximum height; kinetic energy is greatest just before the oyster strikes the ground. Conservation of Energy • When energy changes from one form to another, the total energy remains unchanged even though many energy conversions may occur. • The law of conservation of energy states that energy cannot be created or destroyed. • So in a system the energy you started with is the same amount you end up with. Conservation of Energy • The law of conservation of energy means that when energy is being used, it is not being used up. • Instead, it is being changed from one form into another. • A car engine burns fuel, converting the fuel's chemical energy into mechanical energy to make the car move. Energy Transformation Directions: Each object starts with electrical energy but it converts that energy into another energy. What energy type does it convert into? Thermal, Mechanical, or Electromagnetic Energy Worksheet • This worksheet ties in Energy, Work, and Power. • These are the three concepts you should know the most about after UNIT 4 and 5. • Let’s work on this together as a review. Kinetic Energy • What is the kinetic energy of a jogger with a mass of 65 kg traveling at a speed of 2.5 m/s? • What is the mass of a baseball that has a kinetic energy of a 105 J and is taveling at 10m/s? • What is the kinetic energy of a 0.5kg ball traveling at a speed of 40 m/s? Gravitational Potential Energy • Find the Gravitational Potential Energy of a light that has a mass of 13 kg and is 4.8 m above the ground. • A marble is on a table 2.4 m above the ground. What is the mass of the marble if it has a Gravitational Potential Energy of 568 J? Exit Slip • Windmills make electricity. • What energy forms are converted to make this energy? Exit Slip: Answer • Windmills change the wind's energy into mechanical energy to turn turbines, which then produce electricity.