Feedback 12

l I recall you saying that nuclear bombs are more effective when detonated above the ground (I believe you said 1,800ft for Little Boy). Why is this? Why does this create the most destruction?

excellent question.. I'll have to check on the height, I believe it was higher. Anyhow the idea is right, in that if you think about a weapon having a fixed amount of (destructive) energy, that propagates out in a sphere, then if it starts on ground lots of stuff in the way early on. In the air you can have the massive energy more dispersed before destroying things. Does that make sense? It's sort of like the heat from a lightbulb is really intense right next to the bulb but if you move your hand away it will heat up a larger area, just not as much. The other point is that the nuclear fall-out (some of the worst radiation and long term destructive elements to humans) will propagate much further. Basically you're maximizng the area over which your energy is still leathal.

Class is going great, I think the most helpful review would contain the equations that we need and more information on neuclear weapons than anything else.

well hope it worked out. No equations necessary for nukes... but based on your suggestion I did cover the 2 important equations in class (lens equation and ideal gas law).

(1) Can you give us an update on our grades again after this test? That would be great to start planning study time for finals!

yes

(2) I really liked watchig the videos before class started this week. That was a nice transition from sitting to starting class. Plus they were really interesting too.(3) This weeks' simulations weren't very useful. At least not as much as previous weeks.

fair enough. We work on improving the simulation and keep the vids.

(4) I really have had some problems with this week. First of all I didn't care so much for the topic. In previous weeks I was always able to get an engineer of some sort to help me with the concepts. But, unfortunately I don't know any nuclear physicists. Additionally Tuesday's help sessions could only do the first 2 our of like 6 problems because that was all of the material we'd covered in class. Then you cancelled the session Thursday and I'm unable to come to Friday sessions. It was just really frustrating between the lack in help from the help sessions and now knowing anyone who knew nuclear physics.And in addition, classes went really fast. I know i didn't do well on the homework this week but I'm most upset that I didn't really have the tools with me to help me. The book wasn't much of help either.Anyways, thanks so much

thanks for letting me know. Importantly, however you should contact me and let me know if you're struggling. Both I and the TA"s are available in person and online. If the office hours / help sessions don't work, please set up another time.I'll also work on the pacing of the class.

When I first read the chapter for this week's class, I was really confused on the whole second half. But, after both classes, I feel pretty confident on my knowledge of nuclear weapons. I like how, as usual, the basic ideas are ones that are reiterated in many subjects throughout the course of the class.

that's what this class is about... it is critically important that you realize that basic ideas thread through the entire course... nice job.

I was a little disappointed in the fact that I lost 1.5 points on HW10. I got help on both the problems that I missed and [one of the people at session] checked both of those answers. I am kind of mad that I went to help session, got my reasoning and equation and answer checked, and got the answers wrong.

fair enough... please feel free to have us (me or James) review your work.

i thought this week's hw was just about right. it wasn't too hard if we thought about it long enough, although the quantum physics of how alpha decay works(tunneling) is difficult to wrap my head around. i also thought the simulation was extremely useful in understanding what's going on during fissio

nice to hear. thanks.

I thought class last week moved a little fast again. It seems like the material for this test we touched on a little of each subject, but there is no one main category. This i think will make the test easier but studying a lot harder.The homework last week was easy to apply directly what we learned in class to the homework. It usually is a little bit harder. I did have some difficulty trying to solve the math problems. I usually don't have a hard time but I couldn't go to the help sessions, so I was on my own this week :(

again feel free to contact me on-line.... I'll do a better job of pointing out the main themes in the class and how all of these tie together... two of the big themes were on energy and light / radiation (covering film, optics, balloons, weapons)

We should learn how to do similar problems before we are given the homework. The problem with the homework (and why everyone gets such low grades) is that we have NEVER SEEN THESE TYPES OF PROBLEMS. They would be VERY hard, even if you had seen them before. Since we are not pysicists they are extreamly hard. You could sit for a whole day trying to figure out a few problems before you give up. That is what happens on most problems, people just give it up and take a 0. I go to the help sessions, so its no problem for me, but some people cant work that into thier schedule. There should be more hints on the HW telling you how to go about the problem. There could be example problems that show a similar problem answered. But dont throw brand new stuff at us that is 10X harder than the class material and expect us to answer it, or learn anything from it. Its like giving a 3rd grader a calculus problem and expecting them to work it out & learn from it.

I agree with your characterization of homework being more difficult than what we do in lecture and that it is challenging. You should know that it is supposed to be. Also, you are supposed to struggle with it. I don't want you doing mindless excercizes. I want you thinking, wrestling, and challenging these ideas. Yes it is hard. That is why we have help sessions and I encourage (demand?) that ya'll work together. Seems like it is working for you. For students who cant make the 3 days of help session, please make an effort to set up learning teams on your own, check in with me during my other set of office hours, online, contact the TA's. As for 3rd graders learning calc... interesting idea. I know 6th graders can do it (yes I taught calculus to 6th graders), so maybe we should have this as an option... Bottom line is that people raise / lower themselves to the expectations we set. Don't take this as a criticisms. I want you to know that YES this is CHALLENGING, and YES you CAN do it. I am sure ALL of your can SUCCEED. It is a matter of committing to the time and taking us up on our resurces. Thanks for the honest feedback.