Week 4

This week the video will focus on advances in biology. There are two ways that biology can influence the field of robotics. One way is biomemetics where materials found in nature are examined for features and/or approaches that can be applied to a problem. Slow motion photographs of an animals moving have aided engineers in the design of moving machines. Another way is to actually incorporate biological elements into your design. Genetic engineering is an example of this second way to use biology for technical advancements.

 

This weeks video will highlight some of the amazing advances in the field of biology and present some tough ethical issues. A few examples are directly related to our theme of robotics but perhaps the more important take home message is "How should we proceed?". It might be easy to be offended by some of the apparent unfeeling projects for harnessing biology to provide products. However, one should also imagine themselves desperate for the treatment of a disease or in need of a product that becomes essential to everyday life and ask if one would be willing to really restrict our usage of biotechnology.

 

There of course are already battles about the proper treatment of animals on farms. Indeed many people feel that the way we produce meat for the masses is inhumane or methods employed on puppy farms are unacceptable.

 

This course will not resolve this issue and will not attempt to define the correct behavior on these matters. Each person should recognize this as on ongoing responsibility and that your point of view should be reflected in your behavior that is what you buy and consume and how you vote.

 

TED TALK

Paul Root Wolpe: It's time to question bio-engineering

Web References

TED TALK

Paul Root Wolpe: It's time to question bio-engineering

 

HYPERLINK "http://www.ted.com/talks/lang/eng/paul_root_wolpe_it_s_time_to_question_bio_engineering.html"http://www.ted.com/talks/lang/eng/paul_root_wolpe_it_s_time_to_question_bio_engineering.html

Lec7Week4

Wed 7:30 Physics and Chem. 2378

 

Next we cover momentum and energy.

 

 

 

Momentum

 

 

One way to describe motion is to rate an objects momentum. We noted that inertial mass is a characteristic that an object possesses which inform us how difficult it is to move the object. You can ask how hard is it to get a car rolling? Since it has a large inertial mass you need to provide a large push or force to get any appreciable motion.

 

However this cant be the entire story. You might inquire how fast do I need to go? Getting a massive object to move a little might be easier than getting a less massive object to move a lot.

 

In a similar vane one can consider how hard will it be to stop something (bring it to rest). Clearly you must know two things. You need to the inertial mass and the velocity. The product of these two then can be seen to be a measure of motion. This product combines the two characteristics of speed and mass in an essential way. This perhaps gives some insight into the importance of momentum in the study of motion but certainly doesnt identify its central role in analyzing motion. I mentioned at some point that Newton and Galileo were two great minds of science and yet they were working on formulating chapters 1,2,3 of this introductory text book. If we needed to develop all of the appropriate rules and methods in these chapters it would be a major task. However I can identify momentum as a central player in analyzing motion and I can describe how to use the concept. So indeed it will be difficult to ascertain all of the relevance of momentum to motion but you are already starting pretty far along by realizing this quantity is important.

 

An important feature of momentum is that an object that experiences no external forces doesnt change its momentum.

 

This is an example of a conservation law. If you can identify quantities that are conserved in a process the characterization and understanding of what will transpire are typically simpler. Indeed when one studies collisions (naturally a very important problem) the objects that are colliding can be considered as a system (together) and therefore there total momentum is fixed. Thus if one object gains momentum in a collision the other object will loose momentum simple addition but it must be vector addition.

 

2-object collision

 

There is a quantity that can be identified with the change in momentum the impulse.

 

Several examples of the meaning of this equation can be found in the text. Clearly the equation tells us that to change the momentum of an object you can vary the force and the time as long as their product remains the same. Large force short time has the same effect as small force long time if the products are the same.

 

Take Home.

momentum

quantity that characterizes motion

It is a vector quantity so it follows the rules of vector addition.

No external forces then total momentum is unchanged.

An impulse will change the momentum

 

While momentum is an important tool for understanding and describing motion our primary focus in this chapter will be energy.

 

We start with the idea of mechanical energy. We can then add the other many forms of energy: chemical, electrical, solar, wind. These, for example in the case of wind, can be just a form of mechanical energy or alternatively in the case of chemical energy a new way to store energy.

 

 

Thursday Start a discussion of energy. The following tables were constructed to group ideas together and summarize. Not all of this information was covered. The topic of energy will continue through week 5. Our goal is to understand the basic forms and then to use our understanding to evaluate energy usage and sources.

 

Lec8Week4

Test Tuesay Oct 11,2011

 

 

Asteroid 10 miles wide at a speed of 20 mps 100 terataon = 100 e12 tons of TNT

An explosion occurs when a great deal of stored energy is suddenly converted into

heat in a confined space.

Energy is the ability to do work.

Energy: anything that can be turned into heat.

Heat changes temperature random KE

 

Units calorie, Calorie(food)=1 kcal, joule, kilowatt-hour

1 cal =4.184 J {1 CAL=4.184 kJ} [1 cal 1 gm water 1oC

Wh=(J/s)*(3600 s)= 3.6 kJ ~ 1 Cal

Electricity $0.10/kWh

Efficiency percentage conversion to useful energy

Battery 85%

Gasoline 20% (80%) lost as heat

 

 

 

Energy per gram

(see Physics for Future Presidents)

object

Calories

(~Watt-hours)

Joules

 

Versus TNT

bullet (at sound speed- 1000 ft/s)

0.01

40

0.015

battery (auto)

0.03

125

0.05

battery (rechargeable computer)

0.1

400

0.15

battery (alkaline flashlight)

0.15

600

0.23

TNT (the explosive trinitrotoluene)

0.65

2723

1

modern High Explosive (PETN)

1

4200

1.6

chocolate chip cookies

5

21000

8

coal

6

27000

10

butter

7

29000

11

alcohol (ethanol)

6

27000

10

gasoline

10

42000

15

natural gas (methane- CH4)

13

54000

20

hydrogen gas or liquid (H2)

26

110000

40

asteroid or meteor (30 km/sec)

100

450000

165

uranium-235

20 million

82 billion

30 million

Note: many numbers in this table have been rounded off.

For burning reactions (oxidation) that require the addition of oxygen the weight of the oxygen is not included. For a cookie this reduces the C/gm to 2.5. TNT is a self contained reaction no external matter required.

Burning gasoline results in carbon dioxide and water vapor few other gases. No appreciable solid residue to vent.

Adding efficiency gasoline is 80 times better than batteries.

 

fuel

market cost

cost per kWh

cost if converted to electricity

coal

$40 per ton

0.4

1.2

natural gas

$10 per million cubic feet

3

9

gasoline

$3 per gallon

9

27

electricity

$0.10 per kWh

10

10

car battery

$50 to buy battery

21

21

computer battery

$100 to buy battery

$4.00

$4.00

AAA battery

$1.50 per battery

$1,000.00

$1,000.00

 

 

 

Electric car

6,831 rechargeable lithium-ion (computers batteries). The car range is 250 miles.

Charge the batteries from your home power plug, that driving

the car costs 1 to 2 cents per mile. Top speed: 130 miles per hour.

 

Add replacement costs

Car batteries $4/kWh

Gas (cost fo gas)

 

Hydrogen

hydrogen the only waste product it produces is water, combined with oxygen from the air to make H2O (water). Moreover, the conversion can be

done with high efficiency by using an advanced technology called a fuel cell to convert the chemical energy into electricity.

 

Liq H

3 x more energy per gram (weight)

3 x less energy per gallon (volume)

1 kilogram of hydrogen ≈ 1 gallon of gasoline

 

Because there are few sources of free hydrogen

hydrogen is not a source of energy.

It is only a means for transporting energy.

Can convert CH4 methane via heat + water but you release CO2

 

 

 

 

Gas

Currently supplies around 15% of the global electricity demand.

3.9 - 4.4

Coal

Currently supplies around 38% of the global electricity demand.

4.8 - 5.5

Nuclear

Currently supplies around 24% of the global electricity demand.

11.1 - 14.5

Wind

Currently supplies approximately 1.4% of the global electricity demand. Wind is considered to be about 30% reliable.

4.0 - 6.0

Geothermal

Currently supplies approximately 0.23% of the global electricity demand. Geothermal is considered 90-95% reliable.

4.5 - 30

Hydro

Currently supplies around 19.9% of the global electricity demand. Hydro is considered to be 60% reliable.

5.1 - 11.3

Solar

Currently supplies approximately 0.8% of the global electricity demand.

15 - 30

Tide

 

2.0-5.

Atmospheric Cold Megawatts

 

.03 - 1.0

Thermal Electric

 

3.-15.

OTEC (Ocean Energy Thermal Conversion)

 

6.-25.


 

Forms of Energy

 

KE

Energy of Motion

Gravity PE

Lift a ball Ball can drop and do work {stored in gravitational field}

Chemical PE

Build or break atoms or molecules 2H2+O2=>2H2O releases energy

related to the structural arrangement of atoms or molecules.

Nuclear

Nuclear PE base on nuclear forces i.e. the glounic fields

Thermal

Random KE

Internal

Thermal plus forms of PE [ kT stored in each DOF]

@ any T KE=3/2 kT per mole

but total internal will depend on extra DOF

PE

Energy stored due to configuration in a field

 

 

Energy Transfer

Work

Transfer via a force through a distance [Lift a ball]

Heat

Transfer due to DT Hot Cold [burner pot of water]

 

explosion

Chemical reaction KE of broken constituents, fly apart, releasing springs (i.e. mouse traps).

TNT

Releases its energy very quickly 1gram release energy in 1 ms. Very high power.

 

energy unit

definition and equivalent

calorie (lowercase)

heats 1 gram of water by 1 C

Calorie (capitalized)- the food calorie -also called kilocalorie

heats 1 kg of water by 1 C 1 Calorie = 4182 joules ≈ 4 kJ

joule

1/4182 Calories ≈ Energy to lift 1 kg by 10 cm ≈ Energy to lift 1 lb by 9 in

kilojoule

1000 joules = 1⁄4 Calorie

megajoule

1000 kilojoules = 106 joules costs about 5 cents from electric utility

kWh (kilowatt-hour)

861 Calories ≈ 1000 Calories = 3.6 megajoules costs 10 cents from electric utility

BTU British Thermal Unit

1 BTU = 1055 joules ≈ 1 kJ = 1⁄4 Calorie

Quad

A quadrillion BTUs = 10e15 BTU ≈ 10e18 J Total US energy use ≈ 100 quads per year; total world use is ≈ 400 quads per year

 

value

equivalent

example of that much power use

1 watt

1 joule per second

flashlight

100 watts

bright light bulb; heat from a sitting human

1 horsepower

(1 hp) ≈ 1 kilowatt [A]

A typical horse (for extended time) human running fast up flight of stairs

1 kilowatt

(1 kW) ≈ 1 hp {B}

small house (not including heat); power in 1 square meter of sunlight

100 horsepower

≈ 100 kW [C]

small automobile

1 megawatt (MW)

1 million (1e6) watts

electric power for a small town

45 megawatts

747 airplane; small power plant

1 gigawatt = 1 GW

1 billion (1e9 watts)

large coal- gas- or nuclear power plant

400 gigawatt = 0.4 terawatts

average electric power use US

2 terawatts

= 2e12 watts

average electric power for World

 

 

 

A more precise value: 1 hp = 746 watts

B more precise value: 1 kW = 1.3 hp

C more precise value: 100 hp = 74.6 kW

 

 

chemical potential

More a convenient catch all for Thermodynamics than a form of energy in that it includes all configurations even density related configurations. i.e. monotonic ideal gas in non-uniform distribution has higher chemical potential where density is highest and can reduce chemical potential by becoming isotropic.

Potential for substance to undergo a change of configuration, be it in the form of a chemical reaction, spatial transport, particle exchange with a reservoir.