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