The Nature of Energy Chapter 5.1
What is Energy? Energy: the ability to do work or cause change
Two Types of Energy All forms of energy fall into two types: kinetic and potential. Potential energy: energy that is stored; also energy that is due to position Kinetic energy: energy that is in motion; also depends on the mass and speed of an object
Potential Energies There are many forms of Potential Energy. – Chemical Potential Energy – Nuclear Potential Energy – Elastic Potential Energy – Gravitational Potential Energy
Chemical Potential Energy Energy stored in the bonds of atoms and molecules. Examples: -Anything that can be burnt (coal, gasoline) -Anything that can undergo a chemical reaction (batteries) -Food
Nuclear Potential Energy The potential energy stored in the nucleus of an atom. Examples: Used in Nuclear Power Plants, Nuclear Submarines
Elastic Potential Energy The energy stored by things that can stretch or compress Ex: Rubber bands, springs, foam, trampolines
Gravitational Potential Energy (GPE) Energy stored by objects due to their position above the Earth’s surface. Equation: GPE=mass * gravity * height Examples: Rock on a Cliff, Roller Coaster on Hill
Kinetic Energies Kinetic energy, if you recall is the energy of motion. It can be calculated with the equation: KE=1/2mv² There are many forms of Kinetic Energy -Radiant (Electromagnetic) Energy -Thermal Energy -Electrical Energy -Mechanical Energy
Radiant (Electromagnetic) Energy Energy in the form of electromagnetic waves. Examples: The electromagnetic spectrum (visible rays, X-Rays, Radio Waves…) Sunlight
Thermal Energy (Heat) The energy of motion of the atoms and molecules of an object. Thermal energy can be transferred from one object to another in the form of heat. Examples: Hot Coffee, Hot Metal, or anything hot.
Electrical Energy The energy of moving electrical charges. Examples: Electricity and Lightning
Mechanical Energy The energy that is possessed by an object due to its motion or due to its position. Mechanical Energy is also the sum of potential and kinetic energy (ME= KE + PE) Examples: A brick held above the ground, roller coaster on a hill, anything that is moving
What type of energy is it? Elastic
What type of energy is it? Kinetic
Chemical
What type of energy is it? Elastic
What type of energy is it?
Chemical
Kinetic
Energy Conversion & Conservation Chapter 5.2
Energy Conversions Energy can be changed from one form to another For example: -Heat can be used to boil water creating steam -The steam is now under pressure -That pressure is released, causing a turbine (fan) to spin The heat has been changed to pressure and the pressure has been changed into motion
The total amount of energy in the universe does not change. Most energy in the universe is converted into heat.
Kinetic energy can be turned into potential and vise versa
As a pendulum swings... On the downswing, its potential energy is converted into kinetic energy On the upswing, its kinetic energy is converted into potential energy
Potential and Kinetic Energy
Remember the Law of Conservation of Energy? So what happens to the energy of the pendulum? Why does it eventually stop? The answer is friction The friction of the object swinging through the air converts the potential energy into heat
What is Work? Work = Force * Distance (or displacement) Work is done if a force makes something move. In other words, when work is done, a change occurs. When work is done and change occurs, energy moves from one place to another or changes form. Unit for work is Joules.
How much work is done? Calculate the work done if 10 N of force acts on the body showing the displacement of 2m? Calculate the work done if John pushes his car with 49 N of force but the car does not move.