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KWLQ • What is Energy? K: What do you know? W: What do you want to know? L: What did you learn? Q: What questions do you have?
KWLQ• What is Energy?
K: What do you know?
W: What do you want to know?
L: What did you learn?
Q: What questions do you have?
Notes: Energy
• Energy is the ability to work.
•Work is done when a force exerted on an object moves that object some distance.
•Work is a transfer of energy
NOTES 98-101
Both work and energy are measured in joules.
Units are: Newtons x meters
or
Joules
Work & energy is force times distance
Two Types of Energy
• Kinetic Energy• Energy
associated with motion
• Ex. Dropping the bowling ball.
• Potential Energy
• Stored energy• Ex. Lifting a
bowling ball to a height.
Kinetic Energy= 1/2mass X velocity squared
Kinetic Energy = ½m x v²
Kinetic energy depends on the square velocity! So at twice the speed the truck has 4 x the energy
A more massive truck has more kinetic energy.
If the truck has a mass of 3,600Kg and a velocity of 10m/s, what’s it’s Kinetic energy?
KE = (½ 3600Kg) X (10m/s)² = 180000J
Equation for Gravitational Potential energy
• PEgrav = mass x gravity x height
or• PEgrav = m x g x h
Another type of Potential Energy
• Elastic PE• PE associated with
objects that can be stretched or compressed.
Elastic Potential Energy
Gravitational Potential Energy
PEgrav = mass x gravity x height
50Kg
10 meters high
PEgrav = 50Kg x 9.8m/s/s x 10m = 4900J
Now calculate Kinetic Energy
KE = (½ 50Kg) X (9.8m/s)² = 2401 J
50Kg
What’s its velocity if it falls for one second?
Kinetic Energy = ½m x v²
• Energy conversion – a change from one form of energy to another form.
Energy conversion cont…
• Most forms of energy can be converted into other forms
• Example: Mechanical energy (running water) can be converted into electrical energy (electricity)
Gas engine
photosynthesis
Heat lamp or hair dryer
Oil electricity via power plant
Food your body
For example burning coal at an electrical power plant converts chemical energy into heat. The heat makes steam which turns turbines mechanical energy to make electrical energy. The electrical energy is converted back into heat (oven), light (lights in the house), and mechanical energy (a car’s engine) when it is used.
Conservation of Energy
• Law of Conservation of Energy: when one form of energy is converted into another form of energy, no energy is destroyed in the process
• Energy can not be created or destroyed
Different Forms of Energy
• Mechanical = motion or position of an object
• Thermal = total energy of the particles in an object (the more energy the more heat is given off)
• Chemical = PE stored in chemical bonds (food)
• Electrical = energy caused by moving electric charges
• Electromagnetic energy = visible light, microwaves, x-rays, and uv light
• Nuclear = fission and fusion
Power• Power is the amount of work done in a given time.
Equation for powerPower = work/time
orPower= force x distance/time
Power cont…..
• Units for Power
Joules/second or…
Watt (w)
Formation of fossil fuels
• In the earth’s crust, under distinct pressure, temperature and geological processes, nonrenewable energy formed from once living organisms.
Common Types of Fossil Fuels
•Coal
•Oil (petroleum)
•Natural Gas
• Fossil Fuels make good fuels because the energy stored in them is abundant and easy to release when heated.
• Methane CH4 (gas)• Ethane C2H6 (gas)• Propane C3H8 (gas)• Butane C4H10 (gas)• Pentane C5H12 (liquid, found in gasoline)• Hexane C6H14 (liquid, found in gasoline)• Heptane C7H16 (liquid, found in gasoline)• Octane C8H18 (liquid, found in gasoline)• Pentadecane C15H32 (liquid, found in kerosene and
jet fuel)• Tetracosane C24H50 (liquid, found in lubricating
oil)
Some common uses of Crude Oil
• Solvents• Fertilizers• Pesticides• Plastics • Diesel fuel• Jet fuel• liquified petroleum gas • plastics
•Kerosene
•Synthetic fibers
•Synthetic rubber
•Detergents
Source: Energy Information Administration