Energy and Energy Resources Sections 1

and 2

What is Energy?

• The ability to do work• Involves motion or position• Work occurs when a force causes an

object to move in the direction of the force

• Energy and workoBoth expressed in joules (J)oWork done = Amount of energy is

involved

Kinetic Energy•Energy of Motion•All moving objects have kinetic

energy•Objects with kinetic energy do

workKinetic Energy = mv2

2m= mass, v = velocity

What are some examples of Kinetic Energy when playing

tennis?• Tennis player

– Steps to serve– Steps to return the ball– Swings the racket

• Tennis Ball– Moves throughout the court

• Tennis player standing still (is there any kinetic energy?– YES, parts of his body are moving:

lungs, heart, eyes, etc

Potential Energy•Energy an object has because of its position or shape

•NO motion

Gravitational Potential Energy

•GPE= energy due to an object’s position above the earths surface

•GPE = weight x height•Expressed in Joules (J)

Mechanical Energy• Total energy of motion and

position of an object• Can be all potential energy• Can be all kinetic energy• Can be both kinetic and potential

energy

•ME= PE + KE

•When potential energy increase (or decreases), kinetic energy has to decrease (or increase) in order for mechanical energy to remain constant

• PE KE

• PE KE

Forms of Energy

•Thermal•Chemical•Electrical •Sound•Light•Nuclear

Thermal

• Higher the temperature faster the particles move more kinetic energy more thermal energy

• Substances with particles further apart have more energy than the same substance with particles closer together

• Number of particles also affects amount of thermal energy too!

Which has the most Thermal Energy and which has the

least?

Chemical Energy•Energy of a compound that

changes as its atom are rearranged to form new compounds

•Form of potential energy•Food consists of chemical

compounds

Electrical Energy•Energy of moving electrons•Power plants produce electrical energy

•Form of kinetic energy

Sound Energy•Caused by an object’s vibrations•Form of potential and kinetic energy

•Particles vibrate and transmit kinetic energy from particle to particle

Light Energy•Produced by the vibrations of electrically charged particles

•Unlike sound, vibrations that transmit light energy don’t cause other particles to vibrate

Nuclear Energy• Energy that involves the changes in

the nucleus of an atom• Produced 2 ways:

Fusion: 2 or more nuclei join together

Fission: 1 nucleus splits apart• Small amounts of matter can

produce large amounts of energy

Energy Conversions Section 5-2

Energy Conversions•Change in one form of energy to

another

•Any form can be converted into any other form of energy

•Often one form of energy is converted into more than one form

Kinetic PotentialPotential Kinetic

•Kinetic energy and potential energy are converted back and forth as the pendulum moves

Machines are Energy Converters

•Machines can make work easier by changing the size or direction of the force required to do the work.

1. Chemical energy is converted to into kinetic energy

2. Kinetic energy to pedal

3. Pedals transfer kinetic energy to gear wheel which transfers to the chain.

4. Chain transfers energy to back wheel which makes you move.

Making Conversions efficient

•Energy Efficiency: comparison of amount of energy before a conversion with the amount of useful energy after a conversion.

VS

Where does the ENERGY go??

How does a roller coaster work? Where does the energy come

from to make the car go along the track? Where does the energy go?

All of the energy put into a process still exists somewhere at the end of that process.

• When energy is used to overcome friction some of the energy is converted into thermal energy.

• Energy is never lost, it just goes through a conversion.

• Try rubbing your hands together…..

Closed System•Well defined group

of objects that transfers energy between once another

•Example: –Roller Coaster

»Track»Cars»Surrounding air

Law of conservation of energy

•Energy can neither be created nor destroyed