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Physics 10062<br />

Professor Ani Aprahamian<br />

Science<br />

Literacy<br />

Chapter 3: <strong>Energy</strong>


<strong>Energy</strong>? Scientific Definition/common usage


The <strong>Energy</strong> Basics: Work, <strong>Energy</strong>, Power<br />

Types of <strong>Energy</strong>, Units of <strong>Energy</strong><br />

Goethe: “<strong>Energy</strong> will do anything that can be done in the world”


<strong>Energy</strong> Basics<br />

<strong>Energy</strong> is the ability/capacity to do work<br />

Work is the transfer of energy……..<br />

Work = force x distance<br />

Units: newton-meters,<br />

Work is done when a force<br />

is exerted over a distance<br />

1 J = 1 N m<br />

A force of 1 N moving a<br />

body over 1 m does 1 J of<br />

work.


<strong>Energy</strong> is the ability/capacity to do work<br />

Work is the transfer of energy……..<br />

….Anything that can be turned into heat<br />

What is heat?


Scientifically Speaking<br />

• <strong>Energy</strong> and force<br />

• Work<br />

– Force over distance<br />

– Equation: W=Fxd<br />

– Joule<br />

• <strong>Energy</strong><br />

– Ability to do work<br />

• Power<br />

– Rate at which work is done<br />

– Equation: P=W/t<br />

– Watts


Amount of <strong>Energy</strong><br />

How much energy is there in a pound of<br />

TNT/dynamite compared to a pound of<br />

chocolate chip cookies?


Conversions…compliments of wikipedia<br />

joule watt hour electronvolt calorie<br />

1 J = 1 kg·m 2 s −2 = 1 2.778 × 10 −4 6.241 × 10 18 0.239<br />

1 W·h = 3600 1 2.247 × 10 22 859.8<br />

1 eV = 1.602 × 10 −19 4.45 × 10 −23 1 3.827 × 10 −20<br />

1 cal = 4.1868 1.163 × 10 −3 2.613 × 10 19 1


What is a calorie?<br />

1 cal= amount of energy required to raise the<br />

temperature of 1 gram of water by one degree<br />

Celsius.<br />

<strong>Energy</strong> in food: Calories<br />

1 Calorie=1000 calories<br />

<strong>Energy</strong> units<br />

1Btu = amount of heat energy required to<br />

raise temperature of one pound of water by<br />

one degree Fahrenheit.


<strong>Energy</strong> per gram of different materials<br />

calories (or watt-hrs) Joules Compared to TNT<br />

bullet (moving at speed of sound,<br />

1000 ft per second) 0.01 40 J 0.015<br />

battery (flashlight) 0.01 40 J 0.015<br />

battery (computer) 0.1 400 J 0.15<br />

TNT (trinitrotoluene) 0.651 2723 J 1<br />

modern High Explosive (PETN) 1 4200 1.6<br />

chocolate chip cookies 5 21 kJ 8<br />

butter 7 29 kJ 11<br />

Gasoline 10 42 kJ 15<br />

methane gas (CH4) 13 54 kJ 20<br />

hydrogen gas (H2) for fuel cell 26 110 kJ 40<br />

asteroid or meteor (30 km/sec) 107 450 kJ 165<br />

uranium-235 20 million Cal 84 billion J 30 million


So, how come we don’t use<br />

chocolate chip cookies to blow up<br />

a building?


The First Law of Thermodynamics:<br />

<strong>Energy</strong> is Conserved


We believe it is a principle of the<br />

Universe that energy cannot be<br />

created or destroyed but merely<br />

changed from one form to another.<br />

<strong>Energy</strong> is conserved total amount of<br />

energy in the Universe is constant.


<strong>Energy</strong> is Conserved<br />

• System<br />

– Closed<br />

– Open<br />

• Law of Conservation of <strong>Energy</strong><br />

– Total energy in system is conserved<br />

– Type of energy vs. total


Open System


Closed System


Power: rate at which energy is converted to<br />

work<br />

Power =<br />

energy<br />

time<br />

Units: Joules per second, J/s, or watts (W)<br />

Familiar units of power:<br />

kilo-watt, kW<br />

1hp = 746 W<br />

<strong>Energy</strong> = power x time<br />

=kWh is what you get charged for…


Example……..<br />

If you eat 600 Calories per day (1 large order of fries) above what your energy needs<br />

How long will it take to gain 20 lbs?<br />

Average 150 lbs person needs about 15 calories/pound under normal circumstances<br />

150 lbs x 15 Cal/lbs = 2250 calories per day<br />

To gain 1 lbs…you need an extra 3500 Calories<br />

To gain 20 lbs: 20 lbs x 3500 Calories=70,000 Calories<br />

70,000 Calories/ 600 Calories/day= 116.7 days or about 4 months<br />

How long would you have to walk to burn off those extra 20 lbs?<br />

Assume you burn about 80 Calories/mile<br />

To burn off 20 lbs…need to burn off 70,000 Calories<br />

70,000 Calories/80 Cal/mi= 875 miles of walking will do it!!


<strong>Energy</strong> Drinks….


<strong>Energy</strong> Drinks….<br />

1. What is it about the drink that provides energy?


What is in 5-hour ENERGY ® ?<br />

5-hour ENERGY ® contains a blend of B-<br />

vitamins, amino acids and essential<br />

nutrients. It contains zero sugar, zero<br />

herbal stimulants and four calories.<br />

Original 5-hour ENERGY ® contains about<br />

as much caffeine as a cup of premium<br />

coffee. Extra Strength contains about as<br />

much as 12 ounces of premium coffee,<br />

while Decaf 5-hour ENERGY ® contains<br />

only as much caffeine as a half cup of<br />

decaffeinated coffee.


Important Terms


Weightlifter Applies a Force<br />

over a Distance


Work = force . Distance


Work is defined as the product of the force acting<br />

in the direction of motion times the distance<br />

moved in that direction.<br />

F<br />

d<br />

NO work is done if the object does not move.<br />

If the force is perpendicular to the direction of<br />

motion NO work is done by the force.


Work done by force


The consequence of doing work on an object is to<br />

give the object energy.


Example of <strong>Energy</strong> Changing<br />

from One Form to Another


<strong>Energy</strong> from fossil fuels<br />

Nuclear power<br />

6%<br />

Hydropower, geothermal,<br />

solar, wind<br />

7%<br />

Natural<br />

Gas<br />

12%<br />

Biomass<br />

11%<br />

Coal<br />

21%<br />

How long will they last?<br />

Why are we using so much oil?<br />

Oil<br />

32%<br />

World


Oil equivalent (millions of metric tons)<br />

3,500<br />

3,000<br />

Oil<br />

2,500<br />

2,000<br />

Coal<br />

1,500<br />

1,000<br />

500<br />

Natural gas<br />

~2% increase/yr<br />

(cleanest and least<br />

climate disturbing<br />

fuel)<br />

0<br />

1950 1960 1970 1980 1990 2000 2010<br />

Year<br />

Global consumption of fossil fuels<br />

Use of oil continues to climb by 1% per year because:<br />

low price (bolstered by huge government subsidies)<br />

ease of use as a motor vehicle fuel


The United States and<br />

Its <strong>Energy</strong> Future


The U.S. & Its <strong>Energy</strong> Future<br />

• Fossil Fuels<br />

– Oil, coal, natural gas<br />

• Renewable <strong>Energy</strong> Sources<br />

– Solar energy, wind<br />

• Base Load vs. Peak Load


<strong>Energy</strong>: Technological societies and standards<br />

of living

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