# Energy is the ability to do work (apply a force over a distance).

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Energy is the ability to do work (apply a force over a distance).
What is energy? Energy is the ability to do work (apply a force over a distance). Any object with energy has the ability to create change. Some examples are changes in temperature, speed, position, pressure, or any other physical variable

• A moving ball has energy because it can create forces on whatever tries to stop it or slow it down. • A sled at the top of a hill has energy because it can go down the hill and produce forces as it goes. • The moving wind has energy because it can create forces on any object in its path. • Electricity has energy because it can turn a motor to make forces. • Gasoline has energy because it can be burned in an engine to make force to move a car. • You have energy because you can create forces.

Energy is measured in Joules (J)
A joule is the energy it takes to move 1 Newton a distance of 1 meter. 1 Joule = 1 newton-meter

Joules One joule is a pretty small amount of energy.
An ordinary 100 watt electric light bulb uses 100 joules of energy every second!

Mechanical Energy Is the energy possessed by an object due to its position or its motion Mechanical energy is either Potential or kinetic energy.

Electrical Energy Is energy made available by the flow of electric charge. Electrical energy is usually derived from other sources of energy. Usually from the production of heat energy, through burning something, which is then used to boil water and produce steam which is used to turn a generator, which produces electrical energy.

Chemical Energy Is the type of energy stored in molecules.
Chemical Reactions can either use or release chemical energy.

Heat Energy, Thermal Energy
Any heat that radiates from a heat source.

Nuclear Energy Coming from the splitting of an atom, or fusing two atoms together, when this happens a huge amount of energy is released. This is used primarily to generate electricity or as a weapon of mass destruction.

Is a form of energy that is reflected or emitted from objects in the form of electrical and magnetic waves that can travel through space. There are many forms of electromagnetic energy including gamma rays, x rays, ultraviolet radiation, visible light, infrared radiation, microwaves and radio waves.

Natural Potential Energy
Don’t forget about Solar Power Geothermal Energy Wind Energy Tidal Energy Hydro Energy Biomass Energy

Potential Energy Potential Energy is energy that an object has due to the position of the object, or due to its unique properties . Ex. Stretched Spring, Ball lifted above the ground, Gasoline, or a piece of wood.

Ep = mgh Potential energy = mass (kg) * gravity (m/s/s) * height (m)
Gravitational potential energy is energy from position. Depends on mass, gravity and height. Ep = mgh Potential energy = mass (kg) * gravity (m/s/s) * height (m)

Kinetic Energy Moving mass can exert forces.
Energy of motion is called Kinetic Energy!

Ek = ½ mv2 Kinetic Energy increases with speed
Kinetic energy increases with mass

Solving Problems A 2 kg rock is at the edge of a cliff 20 meters above a lake. It becomes loose and falls toward the water below. Calculate its potential and kinetic energy when it is at the top and when it is halfway down. Its speed is 14 m/s at the halfway point.

Looking for: Given: Relationships: Solving Problems
…initial EK, EP and EK, EP half way down. Given: mass = 2.0 kg; h = 20 m v = 14 m/s (half way) Relationships: EP =mgh EK = ½ mv2 Assume rock starts from rest.

Solution Solving Problems m = 20 kg Draw a free body diagram. EP = mgh
EK = 0 J EP = (2 kg)(9.8 N/kg)(20 m) = 392 J at top h = 20 m EP = (2 kg)(9.8 N/kg)(10 m) = 196 J half way EP = mgh h = 10 m EK = ½ mv2 EK = 0 J, rock is at rest EK = (1/2)(2 kg)(14 m/s)2 = 196 J half way

7.2 Energy Transformations
Energy can change from one form to another. When energy is lost as one form, it is gained as another.

Systems tend to move from higher to lower energy.
7.2 Energy flow Systems tend to move from higher to lower energy.

7.2 Sources of energy The chemical potential energy stored in the food you eat is converted into simple sugars that are burned as your muscles work against gravity as you climb the hill.

7.2 Units of energy Some units of energy that are more appropriate for everyday use are the kilowatt hour (kWh), food Calorie, and British thermal unit.

Law of Conservation of Energy
Energy can never be created or destroyed! Energy only gets converted to one form or another. This is called the Law of Conservation of Energy!

7.3 Conservation of Energy
Many people are concerned about “running out” of energy. What they worry about is running out of certain forms of energy that are easy to use, such as fossil fuels like oil and gas.

7.3 Conservation of Energy
It took millions of years to accumulate these fuels because they are derived from decaying, ancient plants that obtained their energy from the Sun when they were alive. Because it took a long time for these plants to grow, decay, and become oil and gas, fossil fuels are a limited resource.

7.3 Conservation of Energy
Regular (incandescent) light bulbs convert only 10% of electrical energy to light. That means 90% of the energy is released as wasted heat.

7.3 Conservation of Energy
Other forms of energy, such as thermal energy, flowing water, wind, and solar energy are not as limited.

Where Does Electricity Come From in Our Area?
Fossil Fuel(Coal): 42% Nuclear: 40% Fossil Fuel (Gas): 13% Fossil Fuel (Oil): 1.1 Hydroelectric: <1% Other Renewables: 1.3% WHEN WE USE ELECTRICITY IT DOESN’T JUST COME FROM THE SWITCH, ELECTRICITY IS CREATED BY BURNING FOSSIL FUELS or NUCLEAR ENERGY AND CAUSES POLLUTION AND COSTS MONEY Hydro is usually 10% in TN but because of the drought it was only 4% last year -- that's a really interesting, considering the connection between floods/droughts and climate change

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