Unit 3 Energy and Work
Energy Energy is the ability to do work Energy is all around us There are two basic kinds of energy
The two basic kinds of energy: Potential energy Kinetic energy
Potential Energy Potential energy is stored energy There are two types of potential energy Chemical potential energy Gravitational potential energy
Chemical Potential Energy Chemical potential energy is energy that can be released as the result of a chemical reaction Ex. Matches, food, gasoline
Gravitational Potential Energy Gravitational potential energy is also known as energy of position Gravitational potential energy depends on an object’s weight and height
Kinetic Energy Kinetic energy is energy of motion A moving object has kinetic energy
Kinetic Energy Kinetic energy depends on speed and mass The faster an object is moving, the greater its kinetic energy The greater an object’s mass, the greater its kinetic energy
Forms of Energy There are five main forms of energy Mechanical Energy Electromagnetic Energy Heat Energy Chemical Energy Nuclear Energy
Mechanical Energy The energy in moving things Includes sound
Electromagnetic Energy Energy in moving electrons Includes electricity and light
Heat Energy Energy in moving particles of matter The faster a particle moves, the more heat energy it has All things contain some heat energy
Chemical Energy Energy that holds particles of matter together Energy in fuel such as wood or coal is chemical energy
Nuclear Energy Energy stored in the nuclei of atoms Heat and light from the sun are produced from nuclear energy
Energy Energy can change from one form to another When energy changes form, some of the energy is always changed into heat energy Most of this heat energy is lost as waste
Thermal Pollution Thermal pollution is damage that occurs when waste heat enters the environment
Conservation of Energy Law of Conservation of Energy Energy cannot be made or destroyed, but can only change in form
Scientific Theory A scientific theory is an idea supported by evidence over a period of time The Law of Conservation of Energy is a scientific theory
Matter and Energy E=mc2 Matter can be changed into energy Energy can be changed into matter The total amount of matter and energy in the universe does not change This is explained by the equation: E=mc2
E=mc2 E – energy m – matter or mass c – speed of light
Work Work equals force times distance
Work Work is done when a force moves an object a certain distance If an object is not moved, no work is done
Work Energy is the ability to do work However, energy can be used without doing work
Work For work to be done, the direction of the applied force must be the same as the direction of the motion
Measuring Work To measure work, you must know: The force in Newtons The distance in meters Work can be measured in Newton-meters (N-m)
Joules The metric unit of work is the Joule (J) 1 J (Joule) = 1 N-m (Newton-meter)
Measuring Work When measuring work, you must measure the force applied in the direction of motion
Power Power is the amount of work done per unit of time Power is the rate at which work is done Power = work / time Power = (force X distance) / time
Power The metric unit of power is the Watt (W) 1 Watt (W) = 1 Joule per second (J/sec) 1 W = 1 N-m/sec 1 W = 1 J/sec
Power Large amounts of power are measured in kilowatts (kW) 1 kW = 1000 W