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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