Never ask a woman her weight…but her kinetic energy is fine August 2, 2014Posted by mareserinitatis in math, physics, running, science.
Tags: blerch, gravitation, kinetic energy, mass, physics, runners, running, science, velocity
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Today, I had one of the most awesome runs I’ve ever had. In particular, I sustained a much faster pace than I have over a 3 mile distance.
I couldn’t help but wonder, however, about the factor weight plays in one’s speed. As much as I try not to worry about weight and focus on being healthy, there’s this part of me that thinks it would be cool to lose a bit of weight because then I would go SO MUCH FASTER. Or at least that’s what I tell myself. However, I wondered if maybe I was exaggerating a bit, so I decided to check it out.
While it’s a bit of an oversimplification (that doesn’t take into account muscle tone, lung capacity, hydration, electrolyte levels, altitude adjustment, and the 18 bazillion other things that can affect a runner, even as stupid as that kink that’s still in your neck from last Thursday’s swim (okay, that only affects the triathletes here)), a quick check is to use the kinetic energy equation.
First, of course, we have to assume a perfectly spherical runner. Or a Blerch:
(As an aside, if you don’t know what the Blerch is, you must check out the Oatmeal’s wonderful cartoon on running. We all have a Blerch deep inside of us.) Either way, perfectly spherical things are happy for physicists because of all the lovely simplifications we can use in learning about them. So, if you’re a perfectly spherical runner, remember that physicists will love you.
Anyway, our hypothetical runner will have a mass (m), which is, of course, directly proportional to weight. (Weight, of course, is also referred to as gravitational attraction, so the more you have of it, the more attractive you are, at least from the perspective of the planetary body you’re closest to. Also, it may start to be more attracted to you if your velocity starts to approach the speed of light. Maybe this is why many humans also find runners attractive? Not sure.) The unit of mass is the kilogram. The runner will also have to maintain an average
speed velocity (v), and of course your pace is inversely proportional to your velocity. Your velocity is probably measured in miles per hour by your local race, but since we’re being scientific, we could also use SI units of meters/second. That being said, if you double your speed in one unit, it will also double in the other. There’s nothing fancy that happens because you’re using one unit or the other.
The kinetic energy of our runner, assuming an average velocity, can be written as
(1) KE=½ mv2
If we have the kinetic energy and mass, but want to find out the velocity, we first divide both sides of the equation by the mass and then take the square root of both sides. This leaves us with the following result:
(2) v=√(2 KE/m)
Let’s take an example. If we have a runner who has a velocity of 5 mph (or 2.2352 m/s) and a weight of 140 lbs. (or 63.5 kg). If we use SI units to compute this runner’s velocity, it turns out her initial kinetic energy (KEi) is 158.63 J.
On the other hand, we don’t really need to know how much initial kinetic energy the runner has, in terms of numbers. We can just define it as the quantity KEi. It turns out that physicists are kind of lazy about using numbers, so we’ll try to go without them because, in my opinion, it sort of confuses things. (You’ll see why later.)
How this this help us? Well, if you want to take a drastic example, let’s assume a runner loses half of her body weight.
First, let’s establish that her initial kinetic energy is defined also by an initial mass mi and velocity vi. (These would be the same as the 5 mph and 140 lbs. above.) This means her initial kinetic energy can be written as
(3) KEi=½ mivi2
and her initial velocity would therefore be
(4) vi=√(2 KEi/mi).
If her weight drops by half, we can write this as her initial weight divided by 2:
If we put (5) into our velocity equation (2) as our new mass and keep the same initial kinetic energy, we get
(6) vnew=√(2 KEi/m)=√(2 KEi/(mi/2))=√2*(2 KEi/(mi))=√2√(2 KEi/(mi))
You can see that the last part in six is basically the square root of two times our initial velocity from (3). That means that by losing half her weight, our runner would run about 1.4 times as fast, or 40% faster.
Now what if she only loses 10% of her weight? It turns out that (5) would become
so our new velocity would be the initial velocity times the square root of 1.1, which is about 1.05. Losing 10% of her weight only makes her 5% faster.
After spending time looking at this, I decided that going on a massive diet definitely isn’t going to help me speed up significantly. (In fact, if I manage to go from my current weight to my ideal, I would maybe get a gain of a bit over 1/2 mph.) It’s the fact that the mass doesn’t play as strong a role as velocity does because velocity gets squared and mass doesn’t. If you want to go faster, you are better off practicing running faster.
So please pass the ice cream! I need it for my fartlek recovery.
Maybe divorce is the answer… June 10, 2014Posted by mareserinitatis in career, engineering, family, feminism, research, science, societal commentary, work.
Tags: feminism, hyphenated names, marriage, names, proposals, reviewer comments, sexism, stupid
I think I am going to change my name. It’s very annoying.
My last name, anyway.
If I had it to do over again, the one thing I would’ve done when getting married is to keep my maiden name. Hyphenation was not the best idea by a long shot.
This has been an issue (a lot) because I worked with my husband for so long. I suspect it will die off as we are no longer coworkers. However, one of the most bizarre things that has come up is that I recently received some reviews of a proposal that we wrote before he changed jobs. One of the reviewers noted that as a co-PI, I had the same last name as the PI and so a conflict of interest was a possibility.
My university has a clear and very detailed conflict of interest policy, and I’m not clear how this applies. As far as I can tell, this has nothing to do with conflict of interest as these policies are almost exclusively focused on outside financial obligations. I checked with the funding agency, and that was all they had listed for conflict of interest, as well.
If he were supervising me or vice-versa (that is, one of us was a subordinate), such a scenario would violate internal policies to the university. However, even if he is PI and I’m a co-PI, we both reported to someone else. Further, a PI isn’t necessarily a supervisory role. Do faculty members who collaborate on research supervise each other or collaborate? (My experience says there are very few faculty who view their role as co-PI is that of being supervised by the PI.)
In any case, it’s a completely ridiculous comment to make on a proposal review because we could have been two completely unrelated colleagues who happen to have the same last name. I can think about some of the areas of research I do, and I know of several groups of researchers, particularly in Asia, where many members of the team do have the same last name. I never once jumped to the conclusion that there was a problem with this.
Of course, it’s obviously my fault for the name, so I should probably fix it. Do you suppose it’s cheaper to go through the legal name-change process or to just divorce and quickly get remarried?
senseless self-citation April 28, 2014Posted by mareserinitatis in engineering, research, science, work.
Tags: citations, papers, publications, writing
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When reviewing papers, I’ve tried to make a point of checking to see if the authors are heavily into self-citation. I remember realizing how bad the practice was when I was asked to review a paper with a significant number of citations and realized that 90% of them were self-referential.
Self-citing one’s work isn’t inherently a bad thing, particularly if your sub-field is extremely small and you’ve done a significant amount of work in that field. In that situation, it’s important to point out relevant work, not so much in the sense of, “this was what I did before,” but, “this previous work is relevant to the discussion.” However, not everyone self-cites that way. In some cases, someone will self-cite as much of their previous work as possible to get their h-index up. It may not make sense to do that in certain field, but in some sub-fields of engineering, as well as some other fields, it really can make a huge difference for an early-career professor…particularly if the practice of publishing a bunch of LPUs full of self-citations is the modus operandi.
Beyond that, the practice just really bothers me as it doesn’t make sense. If you’re in a TT position, it seems like what you’d want to do is cite broadly. It helps ensure that you have a strong background in the field and that you have a good sense of what other people are doing. It helps to make comparisons about how your work is unique. Most importantly, though, it helps other authors realize you exist and will hopefully make them curious about your work.
Finally, someone may be flattered that you cited their work. I recently had someone comment to me that they were glad someone read their paper other than the editors…and lead author.
A filtered education March 3, 2014Posted by mareserinitatis in education, homeschooling, math, older son, physics, science, societal commentary, teaching, younger son.
Tags: light, older son, physics, science, science education, teaching, younger son
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The older son is a lot of fun. Despite his statements that he has no desire to go into science, he seems to get and make a lot of science jokes. I know he’s not a scientist, but I feel comfortable that he’s scientifically literate. As he was homeschooled, I’m feeling pretty proud of myself.
I’m more anxious about the younger son, though. This weekend, he brought home his science homework, which focused on optics. The kids were studying filters, and one of the questions asked about what kind of light would you see if you shined a flashlight through a blue filter and then a red one. I asked him what he saw, and he said nothing. Unfortunately, he was told that he saw nothing because the flashlights just weren’t bright enough, but that what he should have seen was purple.
I’m pretty sure that if I had ever been bombarded with gamma rays in the past, I would’ve turned into She-Hulk at that very moment and started smashing things. Fortunately (or unfortunately, if being She-Hulk happens to be a goal of yours), that didn’t happen.
I find it infuriating that, throughout my years of homeschooling older son and teaching younger son math, I have constantly been questioned about my ability to teach them. The implication has always been that I may have a degree, but they are experts on teaching. In fact, this particular teacher attempted to take me to task earlier this year about the younger son’s math curriculum…the same teacher who apparently doesn’t understand that light and pigments work completely differently.
After I managed to calm down, I explained that light filters are like sieves, except that they only let one size of particle pass through: nothing bigger can pass through the holes, but nothing smaller can, either. After this explanation, the younger son was able to correctly explain that the reason he saw no light from his flashlight is that the two filters together had blocked all the light.
I’m going to be watching very carefully to see what kinds of scores he’s getting on his answers and whether the teacher realizes she made a mistake. This was very disappointing. There was a new science curriculum introduced this year, one which I was very excited about. The focus was supposed to be on hands-on, problem-based learning, which is great for science. Despite that, it seems that younger son’s science education may be lacking. What good does it do to have a top of the line science education curriculum (or math…or anything else) when our teachers don’t understand what they’re teaching? And how is it that these same teachers can justify questioning the ability to teach material that some of us understand far better than they do?
There is no crying in science February 7, 2014Posted by mareserinitatis in science.
Tags: a league of their own, baseball, science
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This week has been a real roller coaster. Some great things happened, but some really awful things happened, too: horrible, frustrating, gnashing of teeth type awful. As I was contemplating one of these awful things, this popped into my head:
There may be no crying in baseball, but there is in science…just like sometimes, in science, there is laughter, excitement and giddiness. But when there’s crying, there’s no use trying to convince yourself not to. It will happen; it does happen. And then you get over it and move on, just like the rest of life.
99 bottles of…oops January 28, 2014Posted by mareserinitatis in education, physics, science.
Tags: boy scouts, pascal's law, physics, science, Scientists, teaching, video
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Yesterday, I was helping guide some cub scouts (specifically webelos) through their scientist achievement. One of the things we had to discuss was Pascal’s law. Unfortunately, the instruction set on this was pretty limited: read and discuss. That, to me, means they likely wouldn’t understand it at all, so I felt like a demo was in order.
I decided to demonstrate the pressure change in a beer bottle. The concept is simple: fill an empty bottle with a non-compressible fluid (so water works, air won’t) and tap on the open end with a rubber mallet or even your hand. Of course, you want to do this over a bucket because the sudden change in pressure causes the bottle to break at the weakest point, usually the seam along the bottom, and spill it’s contents.
I did this demo for the first time in front of the kids. (I had ONE bottle of beer. No, I didn’t imbibe in front of them…I used it to bake bread.) It worked like a charm. If I didn’t trust physics so much, I wouldn’t have been okay trying it cold like that.
If you don’t have a beer bottle handy and would like to see this demo, there’s a good video on YouTube:
There are four lights! January 27, 2014Posted by mareserinitatis in physics, science.
Tags: lenses, optics, physics
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It’s hard being a physicist. Pretty much every place you look, you’re seeing some cool physical phenomenon that just screams, “Newton (or some other dead guy) discovered me!” If you’re lucky, the screaming isn’t followed by an apple hitting you on the head. Unless you’re a Klingon who is reciting love poetry; then that might be lucky.
Anyway, one such event occurred when I was looking into my coffee mug, which happened to be filled with hot water and a touch of coconut oil for flavor (and medium-chain triglycerides). Some bubbles were sitting there on the surface, breaking up the layer of oil, and behaving like a lens. There was an interesting image on the bottom of the cup, which you can see below.
As you can see, underneath each bubble, there appears to be something that almost looks like a four on a six-sided die. It took me a second to figure out what was going on. Then I realized that, directly above me, were four lights. If I shift my angle, you can see them quite clearly in the reflection, though the one on the bottom left is partially blocked by my phone.
This was surprising to me because this lamp is newly installed. Our previous lamp in this room had only one light. It took me a bit to realize that this was why I was so surprised to see an image in the bottom of my cup: it really was something new.
At the book fair November 8, 2013Posted by mareserinitatis in science.
Tags: books, science, Scientists
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You could be a teacher October 16, 2013Posted by mareserinitatis in career, education, feminism, research, science, teaching, work, younger son.
Tags: education, high school, higher education, math, teaching, younger son
The older boy snickered.
“I like to think so,” I responded.
There was a brief silence followed by, “Welllll………you’re good at math, and you’re a teacher…maybe you should teach math at a high school!”
What followed was a long explanation about how I just physically can’t handle the idea of teaching K-12. Teaching 6 hours a day, grading, prep, etc. Actually, it’s mostly the teaching. Teaching more than 4 hours turns me into a puddle that can’t function until I’ve had a good night’s sleep. Teaching high school is not the ideal profession for introverts. There’s also the fact that, frankly, it would get boring to teach high school math after more than a year or two. The math is what interests me more than the challenge of helping students to understand (though that is an interesting problem when the material is also sufficiently intellectually stimulating). I think he gets it, but he still likes the idea of his mom as a math teacher.
This did bring to the surface some thoughts I’ve been mulling over. Does he see me as a teacher because he already knows I teach or does gender roles have something to do with it? I’ve been pondering this a lot because I get the sense that there are some academics who really do view teaching through a gendered lens and therefore think I’d be better off at a community or liberal arts college. In fact, I imagine there’s a blog post where I discussed someone telling me as much, but I’m not going to dig it out now.
One thing that has occurred to me is that, if I want people to look at my research, I may actually actively have to avoid things that will stick ‘teacher’ into their heads when they think of me. That is, it’s probably a good idea to actively avoid involvement in education conferences and societies except at a cursory level. Teaching should be kept at a minimum. I enjoy the service work component and the idea of exploring interesting aspects of STEM education. I also really enjoy interacting with students (but not all day long). I don’t like the idea that it means that my other abilities and accomplishments will be overlooked. Maybe that’s taking things too far, but I don’t really know how to cement the ‘researcher’ thing into people’s brains unless that’s the only thing they see when looking at my CV. Maybe once the ‘teacher’ version of me has been wiped clean, it’ll be okay to begin dabbling in serious educational research pursuits.
That’s obviously not what my son was worried about. He simply wants me to have a job I enjoy…and maybe there’s a bit of an ulterior motive as he hopes I’d be home more during the summers. It’s a nice idea, but the other nine months of the year probably wouldn’t be all that enjoyable for me…especially if doing research was secondary, or worse, nonexistent.
All that being said, I think that if I do ever become a math teacher, I want the above tshirt. (You can get it here, if you’re curious.)