Energy!!!

Energy!!!Energy!!!

The Law of Conservation of The Law of Conservation of EnergyEnergy

Energy cannot be created or Energy cannot be created or destroyed; it may be transformed destroyed; it may be transformed from one form into another, but the from one form into another, but the total amount of energy never total amount of energy never changes.changes.

“ “the ability to do work” the ability to do work”

The combination of energy and The combination of energy and matter make up the universe: matter make up the universe: – Matter is substance, and energy is Matter is substance, and energy is

the mover of substance. the mover of substance.

What is energy?What is energy?

Energy is Energy is nature’s way of keeping score. nature’s way of keeping score.

We sense energy We sense energy only when the only when the score changes,score changes,

either a either a transformation transformation from one form of from one form of energy to another, energy to another,

or a transfer of or a transfer of energy from one energy from one point to another.point to another.

How is all energy divided?How is all energy divided?

PotentialEnergy

KineticEnergy

All Energy

GravitationPotentialEnergy

ElasticPotentialEnergy

ChemicalPotentialEnergy

Potential KineticPotential Kineticenergy of energy of position or position or energy in energy in storage.storage.

– Water behind a Water behind a

damdam– Hammer over headHammer over head– Food on the plateFood on the plate

energy of energy of motion, the form motion, the form capable of doing capable of doing workwork – Flowing waterFlowing water– A falling hammerA falling hammer– Electrons Electrons

regenerating ATP in regenerating ATP in a bio’l cella bio’l cell

PE = mghPE = mgh

m = mass m = mass (kg)(kg)

h = height h = height (m)(m)

g = accel due g = accel due to gravityto gravity– (9.8 m/s(9.8 m/s22))

What is Gravitational Potential What is Gravitational Potential Energy?Energy?

o Potential energy Potential energy due to an object’s due to an object’s positionposition

o P.E. = mass xP.E. = mass x height x height x

gravitygravity

Don’t look down, Rover!

Good boy!

What is Potential Energy?What is Potential Energy?

o Energy that is Energy that is stored and waiting stored and waiting to be used laterto be used later

What is Elastic Potential What is Elastic Potential Energy?Energy?

o Potential energy due compression Potential energy due compression or expansion of an elastic object.or expansion of an elastic object.

Notice the ball compressingand expanding

What is Chemical Potential What is Chemical Potential Energy?Energy?

o Potential energy Potential energy stored within the stored within the chemical bonds chemical bonds of an objectof an object

What is Kinetic Energy?What is Kinetic Energy?

o Energy an object has Energy an object has due to its motiondue to its motion

o K.E. = .5(mass x K.E. = .5(mass x speedspeed22))

KE = 1/2 m vKE = 1/2 m v22

4 kg bowling 4 kg bowling ball ball

at 10 m/sat 10 m/s

= .5 (4kg) = .5 (4kg) (10m/s)(10m/s)22

= 200 J= 200 J

.25 kg baseball .25 kg baseball

at 50 m/sat 50 m/s

= .5 (.25kg) (50 = .5 (.25kg) (50 m/s)m/s)22

= 312 J= 312 J

Courtesy Jerry Ohlinger’s Movie Material Store

Work is done when a force is exerted over a distance.

WorkWork

is equal to the force that is exerted is equal to the force that is exerted times the distance over which it is times the distance over which it is exerted.exerted.

W = F x dW = F x d

The unit of work combines the The unit of work combines the unit of force (N) with the unit of unit of force (N) with the unit of distance (m) distance (m)

Newton-meter (N-m) aka Joule. Newton-meter (N-m) aka Joule.

You carry a You carry a 20 kg suitcase20 kg suitcase upstairs, a upstairs, a distance of 4mdistance of 4m. How much work did you . How much work did you

do?do? W = F x d W = F x d

F = ma F = ma

= (20 kg) (10m/s= (20 kg) (10m/s22) = 200 N ) = 200 N

W = F x d W = F x d

= (200 N) (4m) = (200 N) (4m)

= 800 J = 800 J

PowerPower

measures the rate of work done.measures the rate of work done.

or the rate at which energy is or the rate at which energy is expended.expended.

Power is the amount of work Power is the amount of work done, divided by the time it takes done, divided by the time it takes to do it. to do it.

Power (watts) = work (joules) / Power (watts) = work (joules) / time (sec)time (sec)

P = W/t P = W/t

PowerPowerSince work performed equals energy Since work performed equals energy expended, expended,

Power (watts) = energy (joules) / Power (watts) = energy (joules) / time (sec)time (sec)

The watt is defined as the The watt is defined as the expenditure of expenditure of

1 joule of energy in 1 second. 1 joule of energy in 1 second.

(75 watt light bulb consumes 75 J/sec)(75 watt light bulb consumes 75 J/sec)

Important formulas and unitsImportant formulas and units

QuantityQuantity DefinitionDefinition UnitsUnits

ForceForce mass x accel.mass x accel. newtonsnewtons

WorkWork force x distanceforce x distance joulesjoules

EnergyEnergy power x timepower x time joulesjoules

PowerPower work / timework / time wattswatts

Ex. Problem on Power: Ex. Problem on Power: Your CD system, uses 250 watts of Your CD system, uses 250 watts of electrical power. electrical power. You play it for 3 hrs. How much energy You play it for 3 hrs. How much energy used? About how much would it cost?used? About how much would it cost? If one kWh is $.08.If one kWh is $.08.Energy (J) = power (watts) x time (sec) Energy (J) = power (watts) x time (sec) = (250w) (3hr) = 750 Whr = .75 kWh= (250w) (3hr) = 750 Whr = .75 kWhThe cost = 8 cents/ kWh x .75 kWh The cost = 8 cents/ kWh x .75 kWh = 6 cents= 6 cents

6 fundamental forms of energy6 fundamental forms of energy1.1. mechanical energymechanical energy

2.2. Thermal (heat) energyThermal (heat) energy

3.3. electromagnetic energyelectromagnetic energy

4.4. electrical energyelectrical energy

5.5. nuclear energynuclear energy

6.6. chemical energychemical energy

What is the source of our What is the source of our energy?energy?

The source of The source of practically all practically all our energy is our energy is the Sunthe Sun..

What is Mechanical What is Mechanical Energy?Energy?

o Energy due to an Energy due to an object’s motion object’s motion

(kinetic) or position (kinetic) or position (potential).(potential).

The bowling ball has The bowling ball has mechanical energy. mechanical energy.

When the ball strikes When the ball strikes the pins, mechanical the pins, mechanical energy is transferred energy is transferred

to the pins!to the pins!

Examples of Mechanical Examples of Mechanical EnergyEnergy

What is ElectromagneticWhat is ElectromagneticEnergy?Energy?

o Light energyLight energy

o Includes energy Includes energy from gamma rays, from gamma rays, xrays, ultraviolet xrays, ultraviolet rays, visible light, rays, visible light,

infrared rays, infrared rays, microwave and microwave and

radio bandsradio bands

What is Electrical Energy?What is Electrical Energy?

o Energy caused by Energy caused by the movement the movement

of electronsof electrons

o Easily transported Easily transported through power through power

lines and lines and converted into converted into other forms of other forms of

energyenergy

What is Chemical Energy?What is Chemical Energy?

o Energy that is Energy that is available for release available for release

from chemical from chemical reactions.reactions.

The chemical bonds The chemical bonds in a matchstick in a matchstick

store energy that is store energy that is transformed into transformed into thermal energy thermal energy

when the match is when the match is struckstruck..

Examples of Chemical Examples of Chemical EnergyEnergy

What is Thermal Energy?What is Thermal Energy?o Heat energyHeat energy

o The heat energy of an The heat energy of an object determines how object determines how active its atoms are. active its atoms are.

A hot object is one whose A hot object is one whose atoms and molecules are atoms and molecules are excited and show rapid excited and show rapid

movement.movement.

A cooler object's molecules A cooler object's molecules and atoms will show lessand atoms will show less

movementmovement. .

QUIZ TIME!QUIZ TIME!What type of energy What type of energy

cooks food in a cooks food in a microwave oven?microwave oven?

ELECTROMAGNETIC ELECTROMAGNETIC ENERGYENERGY

What type of energy is What type of energy is the spinning plate the spinning plate inside of a inside of a microwave oven?microwave oven?

MECHANICAL ENERGYMECHANICAL ENERGY

QUIZ TIME!QUIZ TIME!Electrical energy is Electrical energy is

transported to your house transported to your house through power lines.through power lines.

When you plug an electric When you plug an electric fan to a power outlet, fan to a power outlet, electrical energy is electrical energy is transform into what type transform into what type of energy?of energy?

MECHANICAL ENERGYMECHANICAL ENERGY

QUIZ TIME!QUIZ TIME!

What energy transformation What energy transformation occurs when an electric occurs when an electric

lamp is turned on?lamp is turned on?

ELECTRICAL ENERGYELECTRICAL ENERGY

ELECTROMAGNETIC ENERGYELECTROMAGNETIC ENERGY

What types of energy are What types of energy are shown below?shown below?

Mechanical and Thermal EnergyMechanical and Thermal Energy((Don’t forget frictionDon’t forget friction))

What type of energy is shown What type of energy is shown below?below?

Chemical EnergyChemical Energy


Electrical, Mechanical andElectrical, Mechanical andElectromagnetic EnergyElectromagnetic Energy


Chemical Energy (yummy)Chemical Energy (yummy)


Thermal EnergyThermal Energy


Mechanical, Electromagnetic, Mechanical, Electromagnetic, Electrical, Chemical and Electrical, Chemical and

Thermal EnergyThermal Energy

The Law of Conservation of The Law of Conservation of EnergyEnergy

Energy cannot be created or Energy cannot be created or destroyed; it may be transformed destroyed; it may be transformed from one form into another, but the from one form into another, but the total amount of energy never total amount of energy never changes.changes.

Education

Energy!!!