Energy! By Amanda Brockbank and Ethan Kessinger Physics Investigation 3

What is energy? According to Conceptual Physics, energy is “That property of an object or a system which enables it to do work.” But what does this mean?

Work Lets start with a key word in that definition: Work Work is the action of putting an object into motion, and is what occurs when we lift a load against gravity (so, the greater the gravity or load, the more work required). Work can be calculated by multiplying force times distance (w=fd) It generally falls into two categories: – Work against another force. For example, when you do a pushup, you are working against your own weight – Work to change the speed of an object. For example, when you speed up or slow down a car. Work is measure in JOULES. One Joule of work is done when a force of 1 Newton is exerted over a distance of one meter. This makes sense when you apply it to the aforementioned formula: work (in joules)=1 Newton x 1 meter. 1 x 1=1. On a larger levels, Joules can be measured as Kilojoules (kJ) or Megajoules (MJ)

Power But what about how long it takes to do that work? Work is an arbitrary number if we don’t have a sense of time. To find how fast the work is done, we use power, the rate at which work is done. Power is calculated by dividing work done by time (power=work done/time interval) – So, if an engine can get 12 joules of work done in 6 minutes, the power is 2 watts As seen above, it is measure in WATTS. One watt is expended when one joule of work is done in one second. Again, this makes sense when it is applied to the formula. FUN FACT: When we watch car commercials and we hear about horsepower, it is actually referring to a unit of power that equals.76 Kilowatts

Energy Forms Now we have broken down the definition of energy, which is a good starting point. But what has energy? Almost everything does! Let’s take a closer looks at the forms Nuclear Radiant Chemical Electrical Mechanical

Nuclear/Atomic Energy Energy is formed from changes in the structure of the nucleus Nuclear Fusion – Two or more atomic nuclei join together to form a single heavier nucleus Occurs in nature – Stars produce heat and light because of nuclear fusion Nuclear Fission – An atom’s nucleus splits into smaller parts Man-made – Take energy from reaction and use it to heat water. This steam is then harnessed as an energy source

Radiant Energy Energy that is transferred by electromagnetic waves, or radiation Includes: Visible light, Gamma Rays, and radio waves Contrary to popular belief, solar energy is not the only way we use the sun. Radiant energy covers all of these mediums. However, you must realize that not all solar energy can be harnessed

Chemical Energy Energy in bonds between atoms Endothermic: Energy required to break bond Exothermic: Broken bonds create new molecules and give off heat *Examples of chemical energy: the body’s use of ATP, and burning of coal

Electrical Energy Presence and flow of an electric charge Current: Movement of the charge Charge: Created by Electrons and Protons

Mechanical Energy The energy due to the position or movement of something. It can be potential energy, kinetic energy, or both

Kinetic Energy Kinetic energy is the energy of motion. It depends on the mass of the object, and the speed of the object. To calculate the kinetic energy of an object, you can use the equation kinetic energy=1/2mass x speed^2. In equation notation, this is fd=1/2mv^2. Remember work? Technically its force times distance. Since kinetic energy is abbreviated by fd, does that mean they’re the same thing? – Work is the act of putting an object into motion, and kinetic energy is simply the energy of motion. They are the same thing.

Potential Energy The energy that an object stores and holds in readiness is called potential energy (it has potential energy because the object has the potential to do work).

Conservation and Transformation of Energy But how does this matter in nature? Well, more than important than simply knowing what energy is, it is important to know how it transforms. The law of conservations of energy states: “Energy cannot be created or destroyed. It can be transformed from one form to another, but the total amount of energy never changes.” In short, energy is never created or destroyed, only transferred from one form to another. We see this all the time in our lives: almost all processes or changes occur partially due to the transformation of energy from one form to another. Any time a change occurs, energy is present. Take, say, something as simple as the solar calculator you use for math: this requires a transfer of energy as light (radiant energy) is transformed to electrical energy.

Conservation of energy This picture shows the transformation of energy coming from the sun as it changes on earth. Clearly, it is never created or destroyed, as the law of the conservation of energy dictates. Rather, the original nuclear energy coming from the sun just changes forms and is transferred from one agent to another.

Machine A device used to multiple forces or to change the direction of forces. Fundamentally, machines are just methods through which energy can be transferred, since in cannot be created or destroyed according to the law of the conservation of energy. 6 Simple Machines: 1.Pulley 2.Lever 3.Wedge 4.Wheel and Axle 5.Inclined Plane 6.Screw

What are the sources of the different types of energy? Chemical Energy: Stored in the bonds of atoms and molecules. Mechanical Energy: Stored in objects by tension (for example, a stretched rubber band is storing mechanical energy) Nuclear Energy: As this is the energy that holds the nucleus of an atom together, it is stored in the nucleus of an atom. Electrical Energy: The movement of electrons and negative charge. Radiant Energy: Found in electromagnetic waves

Energy Sources in the US Clearly, most of our energy comes from fossil fuels. However, if you trace this back further, you will find that most of the energy we use today actually comes from the sun. There is the obvious use of solar energy, but when we burn any sort of fossil fuel, we are releasing chemical energy that was stored in plants millions of years ago, originally coming from photosynthesis and the sun.

Energy Transfer in Everyday Life Sun Heats the Earth, air rises and creates wind: Radiant energy The wind blows and moves the turbines: Kinetic Energy Turbines rotate that is captured by the generator: Mechanical Energy Generator harnesses energy and stores it: Electrical Energy Wind Turbine