Is our final going be weighted in terms of its comprehensiveness? Is the last chunk of material we are learning going to be emphasized more than the first stuff we learned? That's how we did last semester, and I was just wondering if it would be the same. Thanks Professor Finklestein!

My hope is to weight it evenly across all the material (except perhaps deemphasize MRI's ; ).

I remember hearing a long time ago that it might be possible for our cars to run on corn oil. First of all is this true? Second, how does corn oil differ from the oil we use today in our cars? Thirdly, if it is possible why dont we use it now?

great question. Yes, I don't know all the details, except yes, they work similarly from a physics perspective: converting chemical (potential) energy into thermal energy (inside a cylinder of a car) which pushes your pistons which pushes the rest of the engine, drive shaft, wheels. I'm sure there are many differences, no doubt in refinement etc.. You want to extract all the chemical energy out of the corn oil. It may not be as efficient (worth doing some research!). As to why it is not used... I'm sure it is a mix of technological advancement and politics..

In class today (4/14) you briefly touched on the rule of 70. Can you explain this in more detail? I have heard of it before, but am weary of its use.

Sure... the amount of time that it takes for something (like cost of a hamburger) to double is given by:

Time (in years) = 70 / (growth rate in percent per year).

So if the increase in the cost of hamburgers (or number of people on the planet) is 10% / year, then the doubling time for the cost / population = 70/10 = 7 years. If it costs $5 today. In 7 years it will cost $10. In 14 years (7 years later) it will cost $20... etc etc...

I found the MRI lecture to very very confusing. I really understood the x-rays, but as soon as you got to MRI's I got completely lost.

Right... sorry about that. You are still responsible for undertanding the very basics. That MRIs set up a strong magnetic field (from big external magnets) that align all the hydrogen atoms in your body (their protons). Then you can probe where the hydrogen atoms are by sending in radio waves (which will cause the hydrogen atoms to flip magnetic spin and absor the radio waves). Where there are Hydrogen atoms the radio waves don't pass through your body. So then you get (an inverse) image of where there are hydrogen atoms and it allows you to look at soft stuff in your body (unlike x-rays) which has hydrogen..water, blood, just about everything!

Class is going great!!!! I am really enjoying our new topics. Is there any way you could post a review guide?

great idea... I'll work on doing that.

I really appreciated the Recap of MRIs on Thursday. Tuesday's lecture was too fast to comprehend and the study sheet on MRIs you put up online was perfect! Short and sweet and it let me know the basic idea of what was happening.

good to hear

I loved THursday's lecture though. It was awesome! I'm not an environmental person at all, but I wish you had directed more of the lecture towards the physics of the environment. eh. I don't know. It was really good though. I've done a lot of work with exponential growth before but this was way cool.

cool... yup... so many interesting things in this class.

I really missed having the homework correction essays.

they're back.

However, I wasn't so much for the "make your own question" essays. I feel like I do the homework to understand the concepts and it was hard to make questions about a topic I didn't feel I fully understood. The idea is good though

yes it is one of the best ways to know that you know something....

.Lastly, I know we would all really appreciate our updated grades, especially updated with our lowest homework and test dropped. It would really help to study for finals. Which, by the way, how would we best study for finals? Lecture notes? Homeworks? Old tests?Thanks!

homeworks, exams, lecture notes.... and yes, I'll provide an updated grade sheet for ya'll on Tuesday.

I really enjoyed the energy and the environment lecture in class. But I left wondering what can be done to delay what is going on, if anything. Do you have any suggestions regarding the conservation of energy?

yes: we can change how we live personally --- how much energy we use. We can also make our voice heard politically. Never be shy to let your opinion be heard by both those around you and those who represent you nationally. Congressional representatives (in the house and Senators) always appreciated hearing from their constituents, especially students. And you can email them!

I thought the two lectures this week were completely different. I found tuesday's lecture on MRI was one of the most difficult this semester. I didn't feel like I understood how they work even after looking over the notes and what we need to know. From my experience at the hw help session this week, it didn't seem like many people understood it at all.

right... see my note above and the response on line on the website... (on weekly assignments sections).

On the other hand, I really enjoyed thurday's lecture. I liked seeing how much longer our current sources of energy will last using the exponential function. When you first put up Prof. AL Bartlett's quote I thought it was stupid, but now I realize how it can be applied to an infinite number of situations.

cool to hear.

I understand that ultasound is used to see an image of a fetus in a pregnant woman, but why is it used in theropy in healing injurys? When I was playing baseball in high school, I had a shoulder injury and needed to go to our trainer every day before practice and games to have an ultasound done on my shoulder. It felt very pleasant because of the heat, and actually made my shoulder get progressively better as the season went on. Why is this, is it just the heat sensation on my arm that made it feel good, or was it my imagination that made me feel better?

No, you're exactly right on... ultrasound does deposit some energy in your body... remember these are sound waves.. so not only can they be used to listen to reflections (imgaing) but they do deposit energy (after all sound is just vibrations in the air right?) ... so these pressure waves enter your body and cause things to wiggle around... this does two things: 1) some of the wiggling of stuff in your body is absorbed energy in the form of heating and 2) it breaks up clots of scar tissue, blood, etc... and helps with recovery.

n I think it should be stressed online or in class that the homework answers contained in "solutions to HW#" (the pdfs) on the "Weekly Assignments" page on the web are MUCH MORE detailed than the "graded answer key" links (which also list solutions). Going back through these detailed solutions is going to be a GREAT help. Before when I got a homework question wrong I was in the dark about how to correct it because the link I was going to didn't convey HOW to get the answer - it just gave the answer without the intermediary steps. Maybe I am the only one that didn't know this difference but I thought I'd mention it anyway.

you've just helped out your fellow classmates quite a deal..I've announced this to class and posted more explicit notes on the web.

h I thought it was nice that you put up a slide on Tuesday that had the most important stuff on MRI's on it. The whole magnetic field thing is still confusing to me, so that helped a little bit. I thought the lecture on Thursday was one of the most important and interesting things that I've learned. Like I already said, I'm angered by the fact that this is the first time I've heard of this. I've heard of exponential decay and losing resources, but I had no indication that we were heading towards running out in my lifetime. I wish I had heard about it before now and I wish that more people would know about it before they turn eighteen too. Unfortunately, I think [there isn't a political awareness action ...]

Well, education should be useful.. I'm glad this is --- It will be all of us who deal with it.

I had a question concerning the presentations in the lab sections. You mentioned that the presentations would be worth about 10 points and I wanted to know if this was part of the paper grade or something totally seperate.

these are additional points.

I thought that the lecture on the misunderstanding of the exponential growth curve was very interesting and thought provoking. Some of those statistics were almost scary especially the projection that airfare will be in the thousands of dollars

sigh... there goes my trip to Europe ; )

I wanted to point out that this weeks homework was quite difficult and that the material wasn't covered very well. I wasn't sure how to do some of the problems.

Right...well please see solutions, help section, or office hours... the MRI's in particular were tough --- see notes above an online website response.