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Energy The ability to do work or cause change Kinetic Energy (KE) Energy of motion Affected by mass and velocity Potential Energy (PE) Stored energy/has the potential to do work or cause change Examples of stored energy from the sun Food Wood Fossil fuels Energy of position Gravitational potential energy Elastic potential energy Law of Conservation of Mass and Energy Energy cannot be created or destroyed Energy can change form KE ↔ PE Where did the energy go???? Work and Power Work is changing the energy of an object Work is done on an object when the object moves in the same direction as the force applied Work = Force X distance Joule = Newton X meter Examples: Power is the rate at which work is done Power = Work ÷ Time Watt = Joules per second Horsepower = Machines A machine is a tool that makes work easier Work in = Work out Machines do not change the amount of work done Machines make work easier by……. Changing the direction of the force applied 1. Changing the size of the force applied 2. Less force, longer distance More force, shorter distance Simple Machines Lever Inclined plane Wedge Screw Wheel and Axle Pulley Lawn mower interactive Forms of Energy Mechanical Thermal Chemical Electricity Electromagnetic Nuclear Energy Transformations A change from one form of energy into another Single or multiple transformations Examples: Toaster Cell phone Running a road race Power Play Thermal Energy, Heat and Temperature Thermal Energy – the total amount of internal energy for all the atoms of a substance Temperature – the average moving energy of the atoms of a substance Heat – the thermal energy that is transferred between objects that have different temperatures (high concentration to low concentration) Temperature Scales (degrees) Fahrenheit Celsius Kelvin Heat Transfer Conduction – movement of heat from one particle of matter to another Good conductors: Poor conductors: Convection – movement of heat by the circulation of fluid currents Warm air/water is less dense – Why? Cold air/water is more dense – Why? Radiation – movement of heat by infrared (electromagnetic) waves Radiation can move through space or matter All objects can radiate heat Heat transfer inter-actives Insulation A substance that slows down or prevents the transfer of heat Example: Thermos Specific Heat The amount of energy needed to raise the temperature of 1 gram of a substance 1º C Every pure substance has a different specific heat calorie The amount of energy needed to raise the temperature of 1 gram of water by 1º C 1 Calorie = 1000 calories Calorimeter measures the amount of heat given off when a substance burns Food Energy How does energy get into the food we eat? How do we get the energy out of food?