What is energy?
Energy- the ability to do work When one object does work on another object, energy is transferred from the first object to the second object. The unit for energy is Joule (J)– just like work.
Kinetic Energy- energy in motion All moving objects have kinetic energy Kinetic Energy = KE = mv 2 2 ▪ M = mass (Kg)v = m/s ▪ Velocity has a greater effect on kinetic energy than mass does (because it’s squared)
What is the kinetic energy of a car that has a mass of 1,200 Kg and is moving at a speed of 20 m/s? What is the kinetic energy of a car that has a mass of 2,400 kg and is moving at 20 m/s? How does this kinetic energy of the car in the above example compare?
What is the kinetic energy of a 4,000 Kg elephant that is running at 2 m/s? At 4m/s?
Potential Energy- The energy that an object has because of the position, shape, or condition of the object Gravitational Potential Energy - When you lift an object, you do work on it. When you do this, you transfer energy to the object and give the object gravitational potential energy. energy stored as a result of position or height. ▪ GPE = weight x height ▪ GPE = Joules (J) Weight = Newtons (N) height = meters (m)
What is the gravitational potential energy of a book with a weight of 13 N at a height of 1.5 m off the ground? What is the gravitational potential energy of a cat that weighs 40 N standing on a table that is 0.8 m above the ground?
What is the gravitational potential energy of a diver that weights 500 N standing on a platform that is 10 m above the ground?
Mechanical Energy- the total energy of motion and position of an object. Both kinetic and potential energy are kinds of mechanical energy Mechanical Energy (ME) = potential energy + kinetic energy (J)(J) (J)
What is the mechanical energy of a book being held in the air that has 100 J or potential energy and 50 J of kinetic energy? What is the mechanical energy of a goose standing on a rock that has 75 J of potential energy and 60 J of kinetic energy?
Thermal Energy- is all of the kinetic energy due to random motion of the particles that make up an object.
Chemical Energy-The energy in a compound that changes as its atoms are rearranged
Electrical Energy- is the energy of moving electrons. (negatively charged particles in atoms) Sound Energy- is caused by an object’s vibrations. Light Energy- Produced by the vibrations of electrically charged particles. Nuclear Energy- The energy that comes from the nucleus of an atom. Fission and fusion
Friction-A force that opposes motion between two surfaces that are touching
Closed System- a group of objects that transfer energy only to each other. Energy is conserved, not destroyed.
Energy cannot be created or destroyed. The total amount of energy in a closed system is always the same. Some energy is always lost to thermal energy (heat). It’s not lost energy.
A machine that will run forever without any additional energy The machine will put out exactly as much energy as it takes in. This is impossible because waste thermal energy always occurs due to friction.
Energy Efficiency - is a comparison of the amount of energy before a conversion with the amount of useful energy after a conversion More efficient = less friction/less lost energy