Laws of Nature Wk4 Envs321 2011

ENVS 321:

Nature of Science & Science of Going Green

Peninsula College

Perry Spring & Brian Hauge

Spring 2011

Physical and Chemical Laws All Biological system controlled by these

o Laws of Motion (Classical Mechanics)

o Newton’s Law of Universal Gravitation

o Thermodynamic Laws

o Gas Laws

o Einstein’s Laws (Quantum Mechanics)

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Scientific “law” A scientific law can often be reduced to a

mathematical statement, such as E = mc²; it's a specific statement based on empirical data, and its truth is generally confined to a certain set of conditions.

scientific theory synthesizes a body of evidence or observations of particular phenomena. It's generally –but not always -- a grander, testable statement about how nature operates.

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Laws of Motion

Newton’s 1st Law (N1L): a body at rest, remains at rest, a body in motion, remains in motion at a constant velocity unless acted upon by a net force

Newton's 2nd law (N2L): the acceleration of a body that is acted up by a net force is proportional to the magnitude of the net force and inversely proportional to the body’s mass

F = m*a => Force = mass * acceleration

if mass remains constant!

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Newton’s Laws continued: Newton’s 3rd Law (N3L): When a 1st body exerts a force

upon a 2nd body, the 2nd body exerts an equal force in the opposite direction on the 1st body.

Paraphrased: for every action, there is an equal and opposite action.

If acceleration = 0, then sum of the forces = net forces = 0

Newton’s Law of Universal Gravitation: any two objects, no matter their mass, exert gravitational force toward one another F = G × [(m1m2)/r²]

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Newton’s Laws continued:

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http://www.youtube.com/watch?v=iH48Lc7wq0U

Kinetics & Mechanics Kinetics provides a mathematical method of analysis of

the physics of mechanics

Velocity (v) : distance / time v=s/t

Acceleration (a) : velocity / time a=s/t2

Mass (m) : the quantitative measure of inertia

Force (F) : Net Force = mass * acceleration F= m*a

Gravity: all bodies which fall near earth’s surface have the same downward acceleration

9.8 meter/sec2 or 32 feet/sec2

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Work, Force, & Energy

Force is to push or pull Ex: push is the force applied to the door marked pull

Work = Force times Distance

W= F * s = m * s / t2

Energy is the ability to do work

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Contrasting Heat with Work Heat is the transfer of energy due to a difference in

temperature.

Work is the transfer of energy by a process other than heat

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Energy

o Kinetic energy

o Potential energy

o Thermal energy

o Magnetic energy

o Chemical energy

o Electrical energy

o Radiant energy

electromagnetic radiation

Mechanical energy

Luminous energy

Nuclear energy

Elastic energy

Sound energy

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the amount of work that can be performed by a force

Many FORMS of Energy:

Key Definitions Potential Energy- energy of position

or stored energy Batteries store chemical energy as

potential energy

Combustion of wood releases stored solar energy giving off heat and light energy

Kinetic Energy- energy of movement Moving wind and moving water can

be mined for their kinetic energy to create mechanical energy which can create electrical energy

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Heat and Temperature Temperature is roughly the average kinetic energy

in a substance

Heat is the process of energy transfer from one body or system to another due to a difference in temperature.

Thermal energy is a form of energy that manifests itself as an increase of temperature.

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Thermodynamic Laws

The zeroth law of thermodynamics allows the assignment of a unique temperature to systems which are in thermal equilibrium with each other.

The first law of thermodynamics mandates conservation of energy and states in particular that the flow of heat is a form of energy transfer.

The second law of thermodynamics states that the entropy of an isolated macroscopic system never decreases, or, equivalently, that perpetual motion machines are impossible.

The third law of thermodynamics concerns the entropy of a perfect crystal at absolute zero temperature, and implies that it is impossible to cool a system to exactly absolute zero.

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Thermodynamics Zero law – heat transfers until equilibrium

warm to cold transfer

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1st Law of Thermodynamics Conservation of energy - can’t be created or destroyed

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http://www.youtube.com/watch?v=BVxEEn3w688

Thermodynamics 2nd law – entropy of the universe is always increasing;

randomness prevails No perpetual motion, no breaking even.

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3rd Law of ThermodynamicsAbsolute zero can’t be reached - who would want to!

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0 o K = - 273 o C = - 459 o F

How Stuff Works: 10 Scientific Laws & Theories You Really Should Know

Entropy

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Units of Energy

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Energy – Matter Equivalence

http://www.youtube.com/watch?v=AgwDNLBRqjQFrom brightstorm.com/science

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Solar Energy for Living things Photosynthesis

Respiration

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Biomimicry & Solar Leaf A Massachusetts Institute of Technology (MIT) research team, lead by Dr. Daniel Nocera,

have created a functioning artificial leaf which in reality is an advanced playing-card sized silicon+catalyst solar cell that can power a house in a developing country for a day using a gallon (3.79 liters) of water and sunlight.

At the 241st National Meeting of the American Chemical Society in Anaheim, California, Dr. Nocera announced that the MIT artificial leaf mimics photosynthesis using inexpensive nickel and cobalt catalysts to perform electrolysis, splitting water into hydrogen and oxygen, and converts energy up to ten times more efficiently than a natural leaf.

“A practical artificial leaf has been one of the Holy Grails of science for decades,” explained Nocera. “The artificial leaf shows particular promise as an inexpensive source of electricity for homes of the poor in developing countries.”

The oxygen and hydrogen can either be passed through a fuel cell to generate electricity, or burned to generate heat. All the leaf needs is water and sunlight, and it will work for at least 45 hours without degrading in performance according to testing done in the lab.

John Turner at the U.S. National Renewable Energy Laboratory developed the first artificial leaf over a decade ago, but it worked for only a day and was too expensive for practical applications.

- 30 March 2011 in GreenMuze 28 March 2011 in InHabit

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Their future is in our hands.As stewards of our children’s planet, we are faced with an incredible challenge. We must lay the groundwork for a built environment that thrives within the reality of increasingly limited resources and foster an economy that serves the triple bottom line.

A tall order to be sure, but not impossible.

When the green building movement’s leading thinkers and practitioners come together to share their deep expertise and dearest hopes, we can leap ahead as a movement and as a society. Living Future, Cascadia’s annual unconference, offers a unique forum for exactly this kind of gathering. .

http://vimeo.com/19904690

Thermal Mass Thermal mass is effective in improving building

comfort in any place that experiences these types of daily temperature fluctuations -- both in winter as well as in summer.

When used well and combined with passive solar design, thermal mass can play an important role in major reductions to energy use in active heating and cooling systems and hence the reduction of greenhouse gas emissions due to fossil fuelburning in power stations.

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Heat transfer Heat transfer is the transition of thermal energy or

simply heat from a hotter object to a cooler object

three methods of heat transfer (convection, conduction and radiation).

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Heat transfer via RADIATION Radiation is the transfer of heat energy through empty

space. No medium is necessary for radiation to occur; radiation works even in and through a perfect vacuum. The energy from the Sun travels through the vacuum of space before warming the earth.

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Heat transfer via CONDUCTION Conduction is the transfer of heat by direct contact

of particles of matter. In other words, heat is transferred by conduction when adjacent atoms vibrate against one another, or as electrons move from atom to atom. Conduction is greater in solids, where atoms are in constant contact. In liquids (except liquid metals) and gases, the molecules are usually further apart, giving a lower chance of molecules colliding and passing on thermal energy.

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Heat transfer via CONVECTION Convection is the transfer of heat energy between a

solid surface and the nearby liquid or gas in motion. As fluid motion goes faster the convective heat transfer increases. The presence of bulk motion of fluid enhances the heat transfer between the solid surface and the fluid.

Two types:

Natural convection

Forced convection

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