The Evolution of Physics by Snively '11
Physics gets harder as you get older, go figure.
Don’t forget to vote for me in the 2008 Blogging Scholarship for $10,000!
I don’t like physics. A lot of people seem to think I do. I’d like to dispel those rumors: I don’t like physics. Lucky for me, there are all sorts of majors here at MIT to choose from that have nothing to do with physics at all. I could be an electrical engineer, I could do brain and cognitive sciences, I could do chemistry or biology, or any number of different things. Which did I choose?
Mechanical Engineering.
I discovered something about mechanical engineering. Apart from physics, it has the most physics. Awesome, I picked a major that essentially is everything that I hate (physics) mixed with everything I love (building stuff).
Working my way through physics problems in high school, freshman year, and now during sophomore year I’m noticing a trend in physics problems: they get harder. Check this out
Junior Year of High School:
This is a nice summary of physics in high school for me:
We have an Honors physics class where nothing is being learned
We have an Asian (15% of the total asian population of my school)
We have an Hispanic (30% of the total hispanic population of my school)
We have a very difficult to build card house
We have a water bottle on said card house
We have more card house on said water bottle
We have the teacher taking a picture of the lack of learning in his class.
Needless to say things got different when I got to MIT.
Freshman Year:
What? You mean the horizontal component down the ramp is a sin instead of a cos!? Whoa dude, whoa.
And then, a little later. . .
Wait, blocks sliding on blocks? Wait, that doesn’t . . . huh?
Sophomore Year:
This is when I realize that mechanical engineering = physics. I think it really struck me that physics was hard when I got this problem in my PSET that’s due next week.
Yep, let’s see, cart attached to wall with a spring, a pendulum attached to the cart, a force applied to the end of the pendulum, and a dashpot between the pendulum and the wall. Suck.
Flipping through my text book, I saw more and more physics, some of which actually would give me nightmares. I’ve scanned one of those nightmarish ones for you to see. Ready? Can you handle this?
AAAAAAAAAAAHHHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!!!! *faint*
*blinks*
My brain just turned to slush looking at the first picture of the cart attached to wall and etc etc.
Not to mention the second.
LOL Physics follows you everywhere!
Ugh, I hate physics too.
But I want to be course 7 so it’s all good. ^^
but…. i like physics :S
…
This seems pretty scary, especially your last picture.
I think the best thing from this is not to feel discouraged from these example but to think that if I can get into MIT I will be able to learn how to solve all of these, hopefully
The harder the problem, the better you feel after being able to solve it, so after solving that last one …
As a non-mechanics major, I’d like to question how useful solving these unrealistic problems is in the long run..
Maybe I’ll just never understand
One thing which gets me when people say “I hate physics” is that they’re usually talking about these kinds of things. Physics != mechanics problems. Physics is about learning how the deepest foundations of reality work. This is physics from 400 years ago, so please don’t judge the whole discipline on it.
(Disclaimer: Yes, I am course 8)
Ivan’s right. Don’t be too scared. The first two are reasonable with some algebra and practice. I can’t speak for the second two being a freshman, but one of the best things about MIT is that there’s always someone who can help you!
physics makes so much more sense to me than chem or bio
I… wanted to be a mechanical engineer?… uh, time to re-think.. what else can I do if I also like to build stuff?
Look, it’s my homework!
*sees last picture*
ah…hehe, nevermind.
Electrical engineers don’t take more physics than course 2’ers? In my school, we take up until Quantum Mechanics, and also tons of math (up until differential euqations and linear algebra) which is way more physics and math than mechanical engineers or any other major… besides physics and mathematics majors themselvers. It’s interesting how you would think at MIT they would take even more!
Btw, when I saw that last problem, my first reaction was, “I can solve this” then, after the first three seconds *cryes a little*
I actually kind of like Physics, but still:
1st picture- I know this (yay for AP Physics)
2nd Picture- okay, I could work with this
3rg picture- uhhhhh…
4th picture- *head spin*
I actually have no idea how well I’m prepared for my major. I want to major in Chemical Engineering (Course 10, that is, if I get in). I get chemistry just fine, but I haven’t exactly had a lot of exposure to fluid dynamics, thermodynamics, and a lot of other stuff I’ve never heard of that I’ll run into.
@Navdeep
Yeah,you’re right about the Qs. posted – I’m currently in 11th (in the CBSE syllabus) and the 1st 2 questions made some sense to me!
However,the last one looked terrible!!
@Snively
Even though I said the 1st 2 looked bearable – I’m the one who has the same thoughts in the resolution part (huh? the horizontal one’s not always cos?!)
Anyway – you could check out our (NCERT)11th/12th grade books:D
Unfotunately,I’m not studying in an American school so I’ll have to try a shot at MIT the harder way (i.e. as a foreign student)
Wow. The first couple I know but the last does look like a picture straight out of someone’s nightmare. I don’t suppose the pink-purple color scheme is there as an attempt to make people feel better about it, instead of a regular black and white, and to distract you from the actual pain of the problem.
Snively, were classes any smaller today due to the release of Wrath of the Lich King, the newest World of Warcraft expansion?
I’m SO challenged…yea for liberal arts! Seeing those problems makes me glad I’m old and all settled in my career which isn’t even remotely related to physics. Good luck to all of you smart MIT’ers and future MIT’ers! Thank you for doing all of those jobs that people like me have no idea how to do…or want to do! Trust me…you wouldn’t want us doing them anyway!
wow I love physics.and cute problems
holy crap. those psets look scary.
yeah, i’m definitely not a huge fan of physics…brain/cogsci is more my thing =]
@ navdeep
you say you can easily solve much harder mechanics problem than these but you can’t comprehend the real intention behind Snively’s post!
So you clearly don’t like physics as much as Walter Lewin!
wow, that looks like a hardcore problem
that’s why you do theoretical physics and not the horrible pulleys/springs/friction/sliding/inclines/tension/impulses/rotational motion…stuff
string theory makes it all better : )
“We have a very difficult to build card house.” D’you mean you “have a very difficult time building a card house”? Sorry, I can’t really control pointing things out.
I would probably understand the questions, but what are you trying to find in the second diagram? There are like, 5 different variables.
Awesome post, by the way. They’re the kind of things I need to wake my brain up.
Sorry the above post was by me.
Those problems are so fun, First two were quite easy but the last one took me some time (after assuming some frictional constants and spring factors).
By the way Snively, did you really had no idea that the horizontal component of a force(F) can be Fsin(angle)?
See you next year and have fun!
@Navdeep
Don’t put the cart before the horse, you have to get accepted first.
And no, I have no problem with the fact that the horizontal force is sine, it’s just that normally it’s cosine, a little counterintuitive.
Also, I’d be curious to see your solution for the cart-dashpot-pendulum one. Did you use Newtonian or Lagrangian mechanics?
@Anonymous
You’re solving for the equations of motion. An equation that describes how the system moves.
according to me, the first two questions are pretty easy third is a bit tough.the 4th is a stupid question as it is all about resolving forces.i finished such types of problems in my iit coaching classes and these problems also come in physics olympiad.If u are thorough in the concepts u can easily solve these.physics is a beautiful subject i wonder why u hate it.(physics is not just problem solving)
Snively, you’ve made me go in my pants. :0
Easy stuff! :p
@Lulu
I mean, each of these was hard the first time I got it. That’s the point, right? Come to MIT, get PSET questions that you don’t understand, solve them, learn.
Also, I’d rather make MIT students look like wusses than be super arrogant and brag about all the physics I know how to do.
@Everybody
The second one isn’t that bad at all, that’s why it’s a freshman year, introductory physics, PSET 1 problem. The third one has all sorts of other stuff in the problem that I didn’t post, including a bunch of stuff about Taylor series and stability.
The last one just looks like a mess. I’ve never tried to solve it, I don’t know how hard it actually is.
What you’ll notice about my entries is that I don’t go into excruciating detail about everything. I’ll give you a picture and a basic description and let you get on with your lives. I could go into a ton of detail about problems I’ve solved and the exact steps I took, but unless I made them colorful or through in some simplification nobody would read them.
Understand that there is often much more behind what I post that I’m just not showing you.
Physics isn’t getting harder, it’s getting better!
as an alum, now grad student, i’ve worked with many indian students (most from an iit) and there is a huge difference in teaching philosophies between the us and india. most indian students are machines when solving sets of equations. they are usually very advanced, having solved many ugly problems before. the difference is, many of them lack fundamental physical intuition and insight into the physics because they are typically taught by the math. intuition and physical insight are sooooooo important for engineers and that is what MIT stresses. so while many indian students have learned to how to solve such problems, they’ve done so at the expense of understanding the underlying physics.
@ snively
yea i understand now what you are saying …
i’m sorry for starting this mess
@re:india- i completely agree with you
This is why I love physics. You can use it to solve problems that are such a mess using underlying concepts that are really simple and beautiful :-D
@re:india
I also agree with u…most of the Indian students are genius in solving any sort of weird set of equations but they are limited in the practical application of this knowledge…
@snively
maybe u wont believe me snively but the first three probs are considered the basic and simple ones for 11th grade students here in my country (india) and we are given stuff that’s sometimes even more stranger than the last picture you posted !!!!
you don’t belive me … ask a student there who has completed his high school in india …
the last picture you posted is “i don’t know what” but “i hope” that will be there in the 12th grade !!!
I actually like physics….and we just learned how that thing equals sin(theta) in class today lol.
Nice post
@ snively
i would also like to say somthing about your previous reply to some other “navdeep” ….
you were saying that the horizontal component is generally cosine ….well to correct you ..it’s not so …cosine comp is the one which is connected with line subtending angle theta..and other becomes sine…
it doenst evn matters that which of the two from cosine and sin you use ..the only thing important is the angle which you use with them…you see we take cosine theta bcoz it’s the angle bw mg nd mg cos theta …yea dat angle is also equal to theta …and if we would have written it like sin(90-theta) it wudnt have been wrong !!!!!!
These problems aren’t that hard. Maybe they’d take a bit of time, but they’re not that hard.
In our AP Physics last year we had a problem which was something like the 3rd picture; we eventually did finish it although it took time. Just be neat on the working so you don’t mess up and confuse two equations (like I ALWAYS do!).
@Snively
Do you like chem?
How much chem is there in Mechanical Engineering?
I don’t think Snively ’11 intended to start a proverbial “pissing contest” about who has the hardest physics class. He intended to show prospective students how things are at MIT compared to many high schools out there. It is simply fact that most high schools do not have a mechanics curriculum at all comparable to that of MIT and Snively makes it clear to students from those high schools that they, too, can thrive here even if they have a modest background in physics.
I really want metal-thing-with-wheels D in the fourth problem to fall off the ceiling. My physics teacher was a rather practical man — none of this ‘massless follower’ business for him.
(To all you physics geniuses: No blasphemy intended.)
Come on snively.
You’re making MIT students sound like wusses. Man up, dude.
@Lulu
and how does “man up, dude” make MIT students sound like…dude? Especially when you say it to another fellow blogger. From this side, I think you’re making MIT students sound like arrogant, juvenile, poorly spoken wusses.
I think there’s a fine line between arrogance and confidence. Certainly, I have to say amen to, “…I’d rather make MIT students look like wusses than be super arrogant and brag about all the physics I know how to do.”
What physics are you currently in Snively?
i LOVE physics.
just sayin’.
I agree with navdeep(the one who said we do such problems in india)….we really do such problems in 11th grade except the last one(that comes in when we prepare for college entrance examz) have a look on the page (3 of 11) http://www.ncert.nic.in/html/pdf/syllabus/syllabus_vol2/03Physics (XI-XII).pdf
I did not expect such a heated debate on… four physics problems. At least, I only would’ve expected a debate to emerge about the physics behind them & how to solve some of them, not about what the problems might represent as symbols for MIT / … whatever you’re all arguing about.
Interesting.
@last ‘navdeep’… Snivelly is right about horizontal components and cosine – angles in math like to be drawn relative to the positive x-axis (like polar coordinates) so for example in conversion from polar to cartesian the x-coordinate is in terms of cosine theta. But, of course, physicists always seem to find a way to do things differently than mathematicians.. *coughdegreescough*
hey, physics rox.
I think such problems (and indeed all other questions in physics or maths) are much easier with the top down methodology approach. It is simple: Look at the whole, break it into a few distinct individual components and solve the problems of these individual problems to finally obtain a coherent whole. For the scanned problem, take each spring as a component and work out free body sketches where several forces interact. Let me know what you guys think of the top down methodology approach.
Cooooooool……
This is really forcing me to study mechanical engineering at college
It’s amazing how nearly anything that Snively posts can be turned into a debate.
Yeah…we also learn how to make CURRY and ROTI PRATA in India…INDIA ROX!!
I I <3 physics and right now my love has compounded because of my upcoming interview(I’m so excited!)
Btw, the 4th diagram is plain evil :S
Oh, and @theNavdeepwho’ssuchagenius,
You sound like a lolcat.
Ugh HTML. ‘Was saying-I just love physics!
hi snively,
can you please have a blog about nanotechnology at MIT? majors, courses, minors, whatever- I just really want to know.
Thank you
it’s okay snively! don’t faint!
@ahana
well ahana i’m just like u -an indian student aspiring to be in MIT after clearing their high schools …well in which state you are in ?
THAT LOOKS SO FUN (AND EFFING IMPOSSIBLE)! I can’t wait to take physics again!
@Snively
Burning question… Do professors usually assign psets over thanksgiving break that are due soon after? Or do you really get to give thanks for a 4-day break from the pset grind?
@ Navdeep (’13?)
if u think speaking only can get u to ur goals then u r wrong…..nothing can be achieved without dedication and hardwork…..
u can try this…do 1 thing just keep saying optimistically to get in MIT……then we will see that the australian research holds good or not
Yeah, I second that last question. I need a break!!
I agree with Oasis-
I dont think people understand the tone of your writing…especially the vertical cosine joke. I dont know what you intended to get from this blog-but I thought it was more of a fun read than anything. (I love the picture)
I admire those who attempted to solve the problems…the comments inpired me to try myself
Thanks, Snively. Now I know that pre-frosh want to do my physics psets for me.
@Cam
Oh no! It seems I made an unintentional pun and can’t even pick it out. Would you enlighten me? (By current I meant its uses in industrial applications and by potential I meant its viability for medicine delivery/hyperthermia/cool MEMS stuff).
@Liz
I was referring to electric current & magnetic fields / potential energies.
@Cam
Haha, that’s very clever!
Great work all you guys trying to make this an MIT-IIT battleground.
mmm.. physics.. *drool*
Reading these blogs just makes me want MIT more. Hope it doesn’t prove too elusive!
/me seconds that reading these just makes one want MIT more.
(/me = /emote in some mmorpg’s rofl)
Oh man, that last physics problem looks so cool. I’m being completely serious, it would be awesome if I actually knew how to do that. Although right now my head just hurts trying to think of where to even start.
(In case you couldn’t tell, I’m a bit of a physics nerd)
Nice house of cards, btw
yeah, I wish I could make a house of cards like that… and that last problem is pretty sweet. Do you get a week to do that one?
@Snively
I think “Navdeep ’13” is justified in writing his class((’13)), he is just trying to speak his goals. Research in Australia has shown that by BELIEVING in and SPEAKING our goals positively and optimistically, we can achieve them much faster than our peers(who are MOSTLY negative and lack confidence in themselves).
Also, we all understand your post, ALL the Navdeeps up there and me too have completed their high schools in India which must have greatly enriched their problem solving skills PLUS the basic understanding of PHYSICS in particular. They will all satisfy “MENS ET MANUS” (I think).
Snively, I think those problems are cool and I like when you put up said problems. :D Also, this is kind of unrelated, but do you know Professor Markus Zahn, and/or about his work with ferrofluid? I am in love with ferrofluid and all its uses, current and potential. If you like a professor’s research and want to know more about it, is it alright to email him/her?
o.O
So now I feel a little more prepared for it MIT accepts me…some of the physics there is vaguely recognizable from my further maths classes here.
Which is comforting. XD
On the other hand, that last problem makes me want to cry. It looks horrible!
@Oasis:
That a word like “hate” can stimulate debate is amazing? Write a blog entry about hating froyo and see how difficult it is to start getting people to argue. :p
uh, sorry. I forgot, no jokes allowed.
@Liz: Do I detect a pun? (“all its uses, current and potential”)
I’m glad to know that at least this time, it’s only the potential applicants who are causing the mess, not MIT students engaged in a flame war. :/
@Snively: but those pictures look a lot better than they would with numbers. Conceptual problems make me happy.
@commenters from India: Indian high school students probably would do these kinds of problems in the 11th grade (though I’m still doubtful about the fourth one, I’m pretty sure that one is reserved for the precocious physicists in Olympiads and such). But guess what– kids in the US taking AP Physics in 11th grade *also* do these kinds of problems! Snively’s taking the courses at MIT because he said in an earlier post (excuse me if I’m wrong) that he didn’t take AP Physics and thus didn’t cover all of this. Besides, not everyone has to love physics.
My point is that if you can solve those problems, go you! Awesome! (Seriously, awesome.) But do you have to tell the world? :/ It’s kind of beside the point of the post.
*Note: this is coming from an Indian student taking AP Physics in the 11th grade. So I know what I’m talking about when it comes to the material in the class, and I’m not hating on Indians– India is pretty much amazing after all.
Still.
@Navdeep
If you think you outsmart the physics here at MIT then why the heck do you apply?MIT is a place for learning and improving not a place for those who have no room for improvement.
Interesting post and interesting 4th problem…
At least you had some practical problems in your class…
@anonymous applicant:
Are you taking B or C? I’m interested to know which one you’re calling comparable. I took B last year, and we definitely didn’t do problems like that third diagram.
For those unfamiliar with the AP program, there are 2 AP Physics courses. B corresponds a basic algebra based physics sequence that at other colleges might be taken by non-science majors to don’t want to deal with the alternative. C is calculus based and corresponds to a class like 8.01 and 8.02 (there’s a mechanics and an electricity and magnetism part) or a sequence that would be required for science or engineering majors at other schools.
I gave the last two problems to my dad for his high school physics students as a “quiz.” They FREAKED. Then I walked in, looked at the paper, and drew a very complicated diagram/ series of equations on the board, muttering the whole time. The answer was 5pi, using various constants and differential equations.
Yeah, I saw a question above and I would like to know the answer too. So, can anyone tell me if professors give physics homework over thanksgiving?
what exactly are you trying to solve for in the last problem? and what are c0, c1, and c2? i showed my physics teacher this for fun and she wants to try to solve it in class one day…but she needs more information first!
@lulu
Please forgive me. I completely owe you an apology. I over-reacted to the lulu who responded deffensively in other posts by Snively. I abruptly took it seriously and not as a joke. Sorry^(forgivness number) =(
@Errina
lol
Ok, this IIT v/s MIT thing is getting ridiculous. Let me (attempt) to clear it up:
IIT students in India seriously have no life! While they are really good at physics and math, that’s all they know! MIT students are so interesting with a WIDE range of interests, while IIT students ONLY know numbers and exams!
Most of my best friends are IIT students and they have no interests in literature, sports, ECS, the world (honestly, they’re obsessed with IIT!).
I used to be one of them untill I got sick of confining myself to only physics and math.
Sure, IIT students are probably the best physics and math problem solvers their age but honestly,only 1 or 2 out of a million IITians are actually interesting outside of their math and physics problems. I should know, I used to be one of *them*.
@Anonymous
c0, c1, and c2 are the coefficients for the damper. You know how F=kx for a spring (where x is displacement)? Well, F=cv for a damper (where c is velocity). It’s the second term in an ODE, or think of it like a second order spring.
As for what you’re solving for, you’re trying to find the equations of motion. We use Lagrangians, but you can use just an ordinary force balance (it’s just scarier). Your answer will be various derivatives of position (position, velocity, acceleration) mixed with coefficients and things. You should have one equation for every degree of freedom (ie, an equation for every cart).
Good luck!
@Vaibhav
Lagrangians rely on the principles of energy. The actual “Lagrangian” is equal to the kinetic energy of a system minus the potential energy of the system.
Basically, break your system down into several “admissible variations” (degrees of freedom, ways things can move, generally x, y, theta, etc). If there are no external forces, all you have to do then is take some derivatives of the Lagrangian with respect to your degrees of freedom and presto, answer. I can’t really describe it all in one paragraph, but it’s kind of magical. Look it up on wikipedia or opencourseware.
awesome thanks…my teacher is going to have so much fun with this haha
I’m looking at the last problem and.. whoa, I thought 8.012 was bad..
The first problem is alright, classical example. The second problem looks like a potential test problem. The third question looks doable, just give me a hour
The last problem…
Is there a point to it?
Physics is more than solving complex system s of forces that give you nightmares. Physics is the science of understanding the universe around us. It is the concepts that defines physics, not the complex nightmarish problems (although those are fun~).
Therefore, physics rocks!
“Physics isn’t getting harder, it’s getting better!” — Colton
Exactly! XD
The second problem deeply disturbs me, but the last one looks like it would be fun to solve.
…
Wait, I left about 20 questions blank on the SAT Physics Subject Test!!! D:
(Is that related? No, but it’s really fun to say.)
Lagrangian Mechanics was so NEAT to use in the last problem. Newtonian mechanics trapped me in MY OWN fabricated set of equations.
(LAUGHS LOUDLY!)
I’ve never done Lagrangian Mechanics – but can anyone give me an idea of how they are (in the sense how different is it from the general Newtonian mech.)?
@Anyone who knows:
What’s the record for no. of comments for any blog entry on the MIT undergrad site??