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.



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

Web References


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


Wed 7:30 Physics and Chem. 2378


Next we cover momentum and energy.







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.


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.



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)






Versus TNT

bullet (at sound speed- 1000 ft/s)




battery (auto)




battery (rechargeable computer)




battery (alkaline flashlight)




TNT (the explosive trinitrotoluene)




modern High Explosive (PETN)




chocolate chip cookies












alcohol (ethanol)








natural gas (methane- CH4)




hydrogen gas or liquid (H2)




asteroid or meteor (30 km/sec)





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.



market cost

cost per kWh

cost if converted to electricity


$40 per ton



natural gas

$10 per million cubic feet




$3 per gallon




$0.10 per kWh



car battery

$50 to buy battery



computer battery

$100 to buy battery



AAA battery

$1.50 per battery






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 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






Currently supplies around 15% of the global electricity demand.

3.9 - 4.4


Currently supplies around 38% of the global electricity demand.

4.8 - 5.5


Currently supplies around 24% of the global electricity demand.

11.1 - 14.5


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

4.0 - 6.0


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

4.5 - 30


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

5.1 - 11.3


Currently supplies approximately 0.8% of the global electricity demand.

15 - 30




Atmospheric Cold Megawatts


.03 - 1.0

Thermal Electric



OTEC (Ocean Energy Thermal Conversion)




Forms of Energy



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


Random KE


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


Energy stored due to configuration in a field



Energy Transfer


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


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



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


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


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


1000 joules = 1⁄4 Calorie


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


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




example of that much power use

1 watt

1 joule per second


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.