Hi everyone. I love physics since i am young.

I am currently a post grad student in physics focusing on theoretical condensed matter physics.

Recently, i went to different Matrikulasi to give talk on theoretical physics.

I show them some basic simulation of Classical Mechanics and the students seems to be very interested in all the simulations.

It is sad that career in physics is never a priority in Malaysia nor it is exposed to the students in any way. Worse still, not much people know about the difference between Theoretical physics and Experimental physics.

Anyway, since this sub forum is still new, I will start the first topic on physics itself.

Certainly, for those who knows physics well, astronomy, material engineering/science, earth sciences, nanotech and others are also physics study as well. There is no clear boundry between all these disciplines and i hope everyone will hop in and discuss anything related to physics.

Doesn't matter you are currently a form 3 student or a Post Doc. Join in!

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Added on June 14, 2009, 11:41 amFor those who are interested with the simulation
go to

MyPhysicsLab


Or just download the whole simulation. (Requires Java)
Simulation

This post has been edited by wKkaY: Jun 20 2009, 04:08 PM

bro i download the myphysicslab y cant i open it after extract it

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Added on June 14, 2009, 12:38 pmi always refer this website to figure how certain stuff works... its very useful for me...

http://www.howstuffworks.com/

This post has been edited by ganabathi: Jun 14 2009, 12:38 PM

hmm. you don't extract it with winrar. You open it with Java.

Just download new Java and install it. You should be able to double click on it then.

Hi i am an engineer. i did do college physics, but a lot of my physic knowledge has ebbed away with time not because of want but because of just not touching it.
anyway Modular, whats the difference between modular and teoretical physics.
If i am not wrong cosmology falls under the latter?

you mean experimental physics and theoretical physics?

Cosmology is a special branch because the scientist in this field is usually addressed as cosmologist instead of physics.

However, to answer your question. Cosmology have both experimental and theoretical part. The theoretical cosmology icon would be stephen hawking.

Experimental work in cosmology is usually data harvesting from satellite, telescope and also work in some specific collider. (this means some part of cosmology is also particle physics as well.)

Theoretical physics and experimental physics exists is all different branches and fields of physics EXCEPT for string theory where only theoretical work exist.

Interesting.

Mind to elaborate more on string theory? I just know it's a theory to unite classical physics(like Newton's Law) with quantum physics.

Quantum physics is a weird field,though.Any good links to learn about them? Kinda interested in it,even it's completely irrelevant to want i study now.

Doing civil engineering,by the way.

Hey, does anyone heard of M-theory or Theory of Everything? The more I discover String theory, the more confused I am.

Quantum physics is so hard to understand.. It doesn't make any sense at all.

This post has been edited by BlueWind: Jun 14 2009, 06:07 PM

Ah, what part of theoretical Condensed Matter are you specialising in?

Cheesenium/BlueWind: M-theory is simply a unified version of 5 (iirc) different string theories [yes there are plenty of variants of string theories]. String theory is currently an approach to unify general relativity (not Newton's Laws) with quantum physics, but well, there are some philosophical issues surrounding it right now, let's say

edit: note the plural, theories. yes string theories. plenty of them around.

There are also other candidate theories, but to be honest everyone's (I am massively exaggerating - but yes the community seems, from my quite distant perspective) now simply waiting for the results from the LHC (CERN) [the big bang machine, machine that will end the world, blah blah blah] to start culling down on the theories available to give some new direction of study I guess. Because frankly, any crazy/non-crazy idea is possible. They just await the test of experimentation [the truth test in science], which the LHC will do [but the LHC won't be able to do much though, it's energy reach is too low to see effects of supersymmetry and stuff which is afaik, a feature of most string theories, believe it or not, for all the talk in the media about how powerful it is and stuff - but they hope to be able to see hints of supersymmetry at the upper end of the energy reach of the LHC. don't expect much till 2012 and beyond though, the LHC will slowly ramp up from this september onwards to the 7 TeV beam hopefully sometime early - middle of next year]

This post has been edited by bgeh: Jun 14 2009, 08:17 PM

you can obtain string theory information online easily. Get to know the basic idea of it first. The string theory is perhas the most controversial theory ever exist.

As a basic rule of science, all of us knows that if you have a theory, you need an experiment to prove or falsify it. But in this string theory, you can say anything, suggest any theory and even claim that you found the realy unification theory. But! no one can prove you theory!

to bgeh, i am doing some specific material research, thin film and multilayer properties.

You?

Don't know what I'm doing yet to be honest. Gravitating towards mathematics/quantum field theory.

But frankly, haven't a clue.

This post has been edited by bgeh: Jun 14 2009, 07:44 PM

you are doing you phd oversea now?

Haha, it is normal to be confused a little bit at first.

Seems you are doing fully theoretical work as well.

Anyway, i don't know much about qft. Only studied basic things in qm like schrodinger equation. You gonna needs mathematics a lot! haha.

I am also doing some basic grid computing besides my physics work.

Heck, if M-theory is successfully proven, I would open my eyes really BIG to see all the teachings change. I really cannot imagine how the world is going to be like if we were to abandon String Theory.

huh? If we do abandon string theory. Life goes on. There are other approach towards unification theory.

The major problem with string theory is that it cannot be proven or falsified as well. What to do?


I am not really into these great n-th dimensions and different stringy theories.

Gravity lor.. How to unify it? Anyway, sorry about the confusion there because I got messed up with M-theory which is the advance name of String Theory and Theory of Everything.

Trust me, if only we all knew the answer. String theory has plenty of brilliant minds working on it (and I mean damn damn brilliant)

Plenty of brilliant people finding that the last 30 - 40 years of research into string theory came to nought, plenty of depressed theoretical physics departments specialising in string theory I'd imagine

But if that ever occurs, well at least it did bring in a lot of beautiful mathematics

@bgeh and modular,
do you think the advent of the computer age has led to a degradation in scientific revolution in comparison to the earlier 20th century where a lot of breakthrough in physic was discovered by many great minds?
or do you think the computer actually is a handy tool to ease work in data colleection and complicated calculations?

Computers are essential nowadays. It doesn't matters whether which field you are working in.

certainly, the ability to crunch enormous amount of data of super computers is proved to be very useful. Perhaps some new idea or insight can be found through the implementation of computer in physics research.

Despite its usefulness, it is not the most important part of physics. The idea to be able to propose new model, solution are much more important.

Like for myself, i am doing some research on grid computing but my supervisor doesn't really like the idea because he thinks that i shouldn't deviate from my real physics research.

i think generalizing PHYSICS discussion is a bit difficult, no? since Physics alone covers a huge area already.

perhaps i will limit the discussion here towards higher level physics instead of kopitiam styled questions. (time travel, e=mc2 those)

more on technical things instead of discussion.

Are you suggesting we split into different fields? HEP, condensed matter, optic, nuclear etc??

i think different level of understanding is more important. It is unlikely that there are enough people to discuss in each research field.

what is your area of expertise modular? care to share? maybe we can take off from there and dispense more specific questions with relation to your research.
hey maybe you can even link us to some reseach papers you have contributed to?

Physics is actually a good degree. How often do you get to spend 3-4 years on something that doesn't have to do with your career?

However, as good as physics is, I seriously think that the passion for physics changes when one comes into contact with professors.

A bad mix of professors whom most are pricks can really pull down your morale. But then again, there are those exceptional few who really ask probing questions that would make you start thinking. I have to say I thoroughly enjoyed the classical mechanics class and its treatment on gravity, why is the law of gravitation 1/r^2 and not some random number and despite the advances in particle physics no one really understands what is gravity.

Why is the Lagrangian and the Hamiltonian so simple yet so powerful in solving problems? Why weren't we thought these tools when when we were younger? Felt stupid and led around by trying to solve problems using forces......................

form 4 this year, very green to this thing called physics.. anyhow, this linear motion thing interest me a lot,

i got a question, is taking physics as a major hard? Coz i want to take it, but then theres this few devilled-fren of mine implenting that physic is so dam hard

At the degree level,physics (pure science) is probably more difficult to understand than engineering (applied science) because it involves a lot of theories. To know whether you have the passion, I would suggest you go through SPM and A-level/STPM (as a gauge). If you have the passion for it, go for it.

is engineering a little connected to physics?

You'll need to use theories and formulas from physics in many aspects/fields of engineering.

Physics was by far my fav subject in high school. I haven't read much about physics for the past few yrs since my career is in IT now.

I love Physics because I enjoy learning how things work, and it is not a subject that requires heavy memorization.

My fav subtopic in Physics is electromagnetic radiation.
My most hated subtopic is Optics (not interested at all).
The subtopic I find most difficult to understand is Electricity (dunno why, it's my weak point)

This post has been edited by socratesman: Jun 15 2009, 07:59 PM

I've been doing some laymen studying on quantum mechanics, general/special relativity, string theory and some cosmology (dark matter, planet/star/nebula/galaxy, how everything came to become everything). Mostly just documentaries and wikipedia.

It is most interesting. I dont really like the math tho, or math in general I wonder if I can go back to school for it (without the math involved hopefully) for it.

too bad it wasnt covered while i was in high school and it was way different cos it was in bm.

Yes,it's more like applying the laws of physics to solve problems.

Perhaps the mathematics involved in Lagragian&Hamiltonian is a bit difficult for secondary school level.
But to be honest, partial differential and other differential equation should be taught at pre-u level.
Well, nowadays if you go through the content of matrikulasi/stpm/a-level... well..

Do you still do physics? Can i know what's your research area?

certainly yes. To be more precise, engineering is a combination of applied physics, chemistry, mathematics, biology etc. Sounds more towards chemical engineering though. lol

Optics can be very interesting at higher level. (no more snell's law etc, lol)
Electricity and magnetism can be difficult at first, but it is essential at any research field of physics. You just have to force yourself go through it.

Wikipedia and documentaries study won't help much in *real* understanding of the physics.

You will certainly need mathematics no matter what cause it is basically the soul of the physics.

QM needs mathematics of undergrad level. Perhaps more difficult in solving some special function.
GR is WORSE. Basically i can say that no one knows about GR in Malaysia. Tensor itself is already a killer.
String theory also same like GR while cosmology is a little bit too general to discuss about its mathematics.

You can do physics by youself but you can't escape from the mathematics.
There are examples in US where they study physics by self study while working as well. They are able to publish paper or proposed some new ideas as well.

Don't give up if you really love physics.

oh sorry i didn't answer your question. I am currently studying the energy distribution, polarization and other properties of specific thin film.

I am still not having any paper yet because i just started my research few months ago.

you?

I am just an engineer in the telco industry but science is my past time, and I know how watered down the science I get from reading wiki, and all those internet sources.
I guess I can google the stuff you mention and throw some questions.

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Added on June 16, 2009, 2:51 amAre you telling us classic mechanics like the Newton Laws are not up to snuff? Care to elaborate?
Those classical formulas have classical calculus proof already.

This post has been edited by beatlesalbum: Jun 16 2009, 02:51 AM

beatlesalbum: There exists an alternative reformulation of classical mechanics in a variational setting, and this is what we call Lagrangian/Hamiltonian mechanics, and they're very useful, and beautiful refomulation, because of the following reasons:

1) The form of the formulas is independent of the coordinate system, i.e. take Newton's laws, and apply it to a cylindrical coordinate/spherical polar coordinate system. You'll find out that the equations change when you change the coordinates. These don't.

2) It incorporates in symmetries very well (Noether's Theorem), and conservation laws are incorporated into the Lagrangian/Hamiltonian. e.g. if the Lagrangian is independent of some coordinate, then you get a corresponding conservation law, or symmetry.

They're widely used in quantum mechanics, where the Hamiltonian is the governing equation, and in quantum field theory, where the Lagrangian is employed heavily.

edit: and no, wiki can be very detailed too, it's just that the maths without an introduction would probably confuse most people.

edit: to add, Lagrange's formulation in the Lagrangian involves a minimisation problem of minimising some quantity called the action. Just think of it as a more complicated version of taking some curve, and using dy/dx to find the minimum of that curve - it's something like that, and Lagrange's formulation allows you to take all the classical mechanics problems we're used to seeing, and then solving for the 'true' trajectory (the trajectory that is actually taken by the particle) by finding the trajectory that minimises this action quantity.

This interpretation (Lagrange's) doesn't really work in quantum mechanics, because we're considering the probabalistic nature of quantum physics. It was a Richard Feynman, which is probably feynman's namesake, that formulated the quantum mechanical equivalent of Lagrangian classical mechanics, or the action principle to something called the path integral formulation, where the particle goes through all possible intermediate states between some initial state A and final state B, weighted by the probability of each intermediate state. feynman's avatar can then be seen as one of the possible paths for some particle interaction [actually to be more precise, it's a 2nd order diagram describing an annihilation and pair production of a particle and a antiparticle], and his avatar is called a Feynman diagram after the man that invented it himself. These Feynman diagrams are used a lot by particle physicists.

I've probably said too much now, but yeah it should give you an idea of what it is, and perhaps I might've also explained feynman's nickname and his avatar

probably final edit: What exactly is the classical calculus proof of Newton's Laws? I think they're taken to be axioms instead.

This post has been edited by bgeh: Jun 16 2009, 06:57 AM

ModularHelmet: personally I prefer that specific discussions go into their own threads, but chat and one-off questions can remain in an "umbrella cover-it-all topic" like this one. Please help me watch this thread, thanks

dont worry. i will take care of this thread.

a general talk on physics is always good as it will give some new insight to people who don't know before this. Hope this will go on well.

So,i guess Eulerian approach is only used commonly in fluids.Does Eulerian approach used in other field of physics?

Just a curiousity.

This post has been edited by Cheesenium: Jun 16 2009, 06:10 PM

No the Eulerian and the Lagrangian approach in fluid dynamics (they're essentially points of view, one an outside observer, the other, an observer following a single fluid particle) is very different from the Lagrangian (a quantity that you have to compute) in mechanics

Isn't optics a subtopic of EM radiation albeit a specialized part

This post has been edited by befitozi: Jun 17 2009, 07:51 PM

Lol just wanna where can I start in increasing my knowledge on physics? I forgot most of the stuff taught in secondary school already.

I know, besides going back to the secondary school textbooks, where else can I start?

Depends on how strong is your basics.

A good physics book which i enjoyed reading is the "Feynman Lectures". Maybe you can start there though if you say you forgot most of secondary level physics, it may be tough.

Since secondary physics is where you left off, I think reading an A-level book would be appropriate as it isn't too hard to understand. If you'd want to get something short, I would suggest reading 'Longman Advance Level Physic' by Loo Kwok Wai (Longman). If you would like something deeper try 'Physics for Scientists and Engineers' by Raymond A. Serway that can be found at our uni library (location: QC23 SER f). Personally, I found those books easy to understand and interesting. All the best!

Edit: Grammar

This post has been edited by Thinkingfox: Jun 18 2009, 02:09 PM

Feynman? I thought this dude.

Hmm. I'll look around for it. Thanks for the heads up.

Lol! Thanks! Nice, there's even the code to look for.

hi, doing my 2nd year physics,
rite now doing newtonian and relativistic and wave vibration and circuit.

Hey, I am a form 5 student.Can I ask my doubt here?

NO!! Only those with PhD in Physics and above can discuss!

Oops. I don't have a PhD in physcis. So even I can't discuss...

LOL..Just kidding, dude. This discussion is open to everyone of all levels. Of course some background reading would be encouraged.

waoh... i am so tired now....
just back from a trip promoting theoretical physics to secondary school studetns...
it is always good to see response from students. well, except for one chinese school which is so damn stupid.

Damm, why weren't you around during my years as secondary school student .... wish that i had exposure to it back then

What happened?

lol, reminds me when there was this one professor, doing bio thingy.. not sure about what, forgot edy.
she came and explain stuff..

It's not up to me also. But I am the first few person to initiate this project.

A bunch of form sixers all totally non responsive to any of our questions even though we already tried our best to communicate with them.

You what's the funny thing? A form 1 boy who happened to be at the venue actually respond to us and asked question which is actually a good question.

This is totally ridiculous. A group of form six students who are studying in a prestigious school are worse than form 1 kid.

on the other hand, matrikulasi is 100x better.

Last time i used to think matrik students are worse than stpm students. Now? Totally opposite view. (i am stpm dude)

I'm now just started Form 6 last month...any ideas how do I understand more on how to solve various linear motion problem[As what I learn the most for now is all linear motion] cause always got so many forces acting on a certain objects, and I'm kinda confuse with Newton's 3rd Law of Motion which is about Action = Reaction, its like when the question as me the helicopter fly up, they give me the G[Acceleration due to gravity], and mass, then they ask me how many force produced for the helicopter to fly up..then i try to relate it like the force pulling the helicopter down should be equal to the force requred for the helicopter to fly up...but at the same time, i think that the helicopter should have high upthrust force if they want to go oppose the gravity...bu the answer turn out to be the force required to go up = to the weight...why i find it confusing


Anyway, I love Science since primary school and was science top scorer till form 3, and in form 4 and 5, my top subject was physics followed by chem and bio...i love physics so much that I often ask teacher a lot of questions but they hardly can answer any of my questions >_<I always took up some read in the internet but also kinda hard for me to understand >_<

And yeah, I got offer for Matriculation, but then i finally choose to go form 6 although they say much harder than matrikulasi, but the main reason for me to go form 6 is bcoz i get to study deeper in science subs especially physics and chem compare to matriculation bcoz i am very interested in physics and wanted to learn more although it is ahrd

This post has been edited by -Max91-: Jun 19 2009, 09:21 PM

Haha it's common to misunderstand what the 3rd law is saying. I hope this helps.

The simplest and the most accurate way of stating the 3rd law is "If body A exerts a force on body B, body B will exert the same magtitude of force on body A" Sounds easy but not easily understood when its used to solve problems.

Take the helicopter as an example. The earth pulls the helicopter towards it and by virtue of the 3rd law, the helicopter MUST pull the earth towards it. Because we are dealing with gravity, the universal law of gravitation applies here and these two forces are N3L pair forces. Sounds easy right? However this is where many people get confused, I quote,


Can you see where you got lost? There is a engine thrust that acts upwards and there is a helicopter's weight pulling downwards and you made them equal. This is wrong because N3L doesn't come into the picture. Think about it, the helicopter's weight is due to the gravitational force exerted by the earth on the helicopter, so which is its corresponding pair force? Shouldn't it be the gravitational force of the helicopter exerted on the earth(helicopter pulls earth)? The thrust is not the corresponding N3L pair force. It's just another force acting on the helicopter in addition to the gravitational force. A N3L pair force must be the same species, I pull earth, earth pulls me, same species of force.

Now then what is the corresponding pair force for the thrust? The engine pushes the air downwards, so what pushes the engine(helicopter)?

The way to solve such problems is to draw free body force diagrams, it's essentially a diagram that shows you what are the forces acting on the body. N3L does not apply here. Why? Just read the 3rd law again. To give you a hint, if I exert a force on a body, I don't feel, I don't experience the force exerted by me. I don't feel my own push when I push someone.

Does it help?

This post has been edited by feynman: Jun 20 2009, 03:50 PM

Erm thanks, kinda get it, so i think it would be the air push the engine upward...and I don't feel the force when i pushing at something because an equal force is pushing at me too..is tat right?

But still one thing not really clear, from previous question, if the helicopter want to take off, so to get the acceleration or velocity or watsoever, i juz have to equate it with the engine trust but not weight?

You do. Newton's 2nd law says: Resultant force = rate of change of momentum of the object

So it's actually upwards thrust - weight = dp/dt (rate of change of momentum)

omg, thanks a lot, totally understand about it....i always too remember the general formula F=ma but i always forget tat the ma was actually rate of change in momentum, that's y i couldn't solve it

one more question, normally in what cases we use newton's 3rd law? cause most of the question always ask on resultant force which the 2nd law can solve almost everything, so far the 3rd law i did was a truck pulling a car, or box and box stick together and force is exert on them >_<

thanks

er..my physics is not that bad..can score 90+/100

p/s.all discussion here about uni level? seem like we do not learn deep for newton 3rd law.I think I should not study it to confuse myself..haha..meybe syllabus different

hi, just started my foundation with physics in my sub. didnt touch this topic for 3 years since SPM. is there any reference book for a pre-u studies?

can you help me this doubt?
why is it U shaped one the magnetic field strength stronger?

another ques




thanks

This post has been edited by vick5821: Jun 22 2009, 07:47 PM


Attached thumbnail(s)

About U-shape, i think the text in the second picture you post explains it. More magnetic flux concentrated in an area.

but i dont understand what is meant by it

Easiest answer to the magnetic field question is the poles of the magnetic field are closest in a U shaped magnet. The closer the poles are the stronger the magnetic field since it doesn't spread out much due to distance.

the magnetic field overlap in U shaped?

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Added on June 25, 2009, 2:34 pmIs a current carrying conductor an electromagnet? not winded with selenoid one

This post has been edited by vick5821: Jun 25 2009, 02:34 PM

Wah, very hard to find malaysians who like this stuff

I don't take physics, but I'm interested in it.
I do maths, including some geometry, topology and functional analysis.
So cannot run from physics application la.
PDEs, Tensors, Hilbert/Banach Spaces...mostly QM related material
Sometimes it's very hard tho, makes me wanna krai

Can't do physics papers because they have like 3-hour labs, NOT FUN.
Unfortunately don't have physics friends to talk to about all this stuff(no maths friends either lol)
Well...malaysian friends anyway.

Well depends on what you do in the 3-hour labs. I personally enjoyed the 3-hours labs of physics in my engineering course in monash university.

This would be a good place to discuss physics, this thread in particular. As it focuses more on the theory, it doesn't really stray afar compared to other threads that were in this section.

Sorry..i am facing problem in physic,.. hope someone can help me >>.<
Thanks
this is the question
The speed of waves in deep water depends only on the gravitational acceleration g, with dimensions and on the wavelength , with dimension L Derive an equation for the speed of wave in deep water, v .

Hi everybody !

It's so nice to see REAL physics alive and kicking ! With that, I meant hot physics stuffs such as relativistic and quantum stuffs, cosmology, ....those modern physics stuffs that we don't learn in school !

Unfortunately, like what have been mentioned earlier, physics were not given its due coverage in Malaysia. Every year, corporate companies bring in Nobel Laureates to give talk...but in what field ? Economy, Peace etc....but not Physics !!! The only one or two which ever made public was Stephen Hawking's talk and the one given by Jocelyn Bell Burnell (my first attendance to a talk be a world famous astrophysicist)

I hope this forum can continue to grow. Keep it growing, guys and gals !

Hi, all ! Its been months since i surf in LYN forum but only today , i found out there is an interesting section in here. I've never thought there is a section in a forum in Malaysia.

I came to like Physics when im around 15 or 16. Well, I like to read those articles about how Physics laws are being applied in new technologies being introduced to the world.

I thought of studying Physics after SPM, but sadly due to objections from parents ( u know lah, hard to find job, and my parents always have the perception that physicists are always loner , bla bla bla) so instead, im now taking Computer Studies.

Anyways, keep up the good work of keeping this section alive. Looking forward for more topics (:

Regards.

which book u guys find out good for MODERN PHYSICS or QUANTUM MECHANICS??

its really sad to know that quantum physics and many other topics is only taught in postgraduate level. theres so much mysteries to what i'm currently learning now in spm level. we seriously lack exposure to practical physics in malaysia.

Ya basically all the physics learn during secondary school is exam-orientated..juz teach u how to score..but not really try to create an interest in physics among students

I'd argue that SPM level physics has too much of practical physics instead of theoretical ones

Agreed,but still,theoretical physics is much tougher.

Even things like fluids mechanics is too much for a high school student.I really doubt a typical high school student will know how to use Bernoulli's Equation.

Soil mechanics is just absolutely horrible. Whole lot more fun than usual mechanics,though.

Borrow book from Uni or library and make your own study..

i doubt they overlap. they r basically just condensed and put nearer to each other, in other words.

i dont think so. can someone plz help to explain this ?

Hi guys I've always loved physics but after reading lots of texts and materials on it I still believe I have an incomplete understanding of the beautiful subject. However, I have taught students from form 4 right to foundation level Physics at university and I feel I definitely can identify the common problem areas for students. I also take a holistic approach to physics which simply means I teach using experiences u already have to make u understand Physics. So if any of you high school or Pre-U students have queries please don't hesitate to ask. I will help or at least point you in the right direction:)

OH, all Physics student here? Hi thar.. I like physics too when in SPM.. lol..

I've got a projectiles question here


A ball is thrown upward from the top of a building with an initial velocity of 70m/s at an angle of 35 degrees above the horizontal. Given that the height of the building is 65m.
Calculate the time for the ball to reach the ground.

My answer is 1.385s.

I hope that i do it right otherwise i will have my scholarship withdrawn and needed to pay an extra RM840.

Thanks for the help

I got 9.57s wor >_< not sure mine correct a not also

It would be easier if you show the steps that you've used to come up with that number and what is the value for g that you have used in your calculation.

You would need to find out how high the ball will get based on the launch parameters. It's not going straight up so you will need to use trigonometry to get the vertical component of the velocity. This information will provide the time it takes for the ball to go up and stop and the additional vertical distance traveled upward from the top of the building. With the new height and the height of the building, figure out how long it takes for the ball to fall to the ground. Add the time for the ball to go up and stop and the time to fall from its new height to get the total travel time.

This post has been edited by Eventless: Sep 14 2009, 03:33 PM

actual answer is 9.57s,i did not understand the question fully ,that is y i got 1.385s

Orh, this is my school Physics Teacher's method >_<
1st, always divide into two components, X and Y

So in this case, since we don't know the displacement(For X), but for displacement(Y), we get is -65m.[Note : I put a negative in front, because the object is projected from a building which is 65m tall, therefore, the final DISPLACEMENT for Y-component is 65, include ngative because it is going in opposite direction]

Then, since you got displacement(Y) = -65m, acceleration,a = -g (Must put negative, because your motion is opposing the acceleration due to gravity) and velocity(Y-component) is 70sin35. Therefore, sub all these value into :-

s = ut + 1/2at^2 [For all Y-component only]


Sorry can't provide you an image, but if you still don't understand I'll draw it out and scan into my com >_<

This post has been edited by -Max91-: Sep 14 2009, 11:03 PM

kenloh, actually your calculation is not wrong. it is part of the solution if you treat the problem as 2 parts.

first part would be travel against gravity from 0 position back to 0.
second part would your 1.385s where the ball travel from 0 to 65m with the help of acceleration.

first part should give u solution of 8.xx seconds.
add up with second part and you will get the final solution.

I also got the answer as 9.570. I can only say, doing physics need exercise to sharpen you mind. It is important to read more books to have new ideas. University level physics can be very tough for normal secondary school students. However, i also found that today secondary school physics seems become to lack of theory. I can even no need to prepared notes to teach my tuition student. IN physics, the concept is the most important part. with one concept right, you can solve many question.

ive fully understood wat u guys r saying,i misinterpret the question wrong thats y i got -9.57 instead of a positive value,i put it as throwing 35degrees down instead of throwing it up

question solved and completed.

This post has been edited by kenloh7: Sep 15 2009, 12:06 PM

I have a thought experiment that i am too lazy to calcualate.
We all know that light speed for an object is quite impossible becuase it requires infinite energy. But here is the question.
There are 2 objects (spheres) in a vaccum.

Object A has a mass of 1Kg and is 100m away from object B, object A has a radius of 0.01m.

How much mass/density does it require for Object B to be to attract Object A so that Object A will accelerate to 99% or 100% (if possible) of light speed before it crashes into Object B.

I have a fairly reasonable idea on how to solve that problem simply by using Newton's law of universal gravitation and some linear kinematics, however I am far too lazy to do the math. Whatever the result, I still don't think it'll be what you're looking for, because when we're talking about speeds near the universal limit we'd have to rely on Einstein's general relativity, which is way beyond my grasp. So perhaps I shouldn't have said anything at all. Funny how that works out.

This post has been edited by pixelsheep: Sep 17 2009, 01:44 AM

hello,i'm new to this discussions.but hope i can join in since it's interesting.i'm doing master in physics in local U.i must admit i'm still in very basic level of physics.
come on,physics is all about basic what.
nice to meet u ppl.

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Added on September 29, 2009, 11:43 amMaggieMee, abt d sphere experiment.
"I have a thought experiment that i am too lazy to calcualate.
We all know that light speed for an object is quite impossible becuase it requires infinite energy. But here is the question.
There are 2 objects (spheres) in a vaccum.

Object A has a mass of 1Kg and is 100m away from object B, object A has a radius of 0.01m.

How much mass/density does it require for Object B to be to attract Object A so that Object A will accelerate to 99% or 100% (if possible) of light speed before it crashes into Object B."

by newtonian physics,
mass of B = 4.5e31 kg if it collides in 1 nanosecond.aprox to mass of sun.
funniest part is mass of A is not used in the calculation.correct me if i wrong.
if got time,i'll try to fuse relativity in it.
nice thought experiment it was.


This post has been edited by freeman_86: Sep 29 2009, 11:43 AM

Hi All!
Physics graduate here.

hope this place doesn't turn into a "help me solve my homework" forum. haha

Erm now I'm learning Resonance, but there's a problem here...what does Natural Frequency actually is? I don't really understand..does it have a value or what? and is the value fix or change?

We learn this in high school haha... Correct me if i'm wrong, natural frequency is simply the frequency that every physical being vibrates at. It's different for every thing. I'm not too sure what happens when resonance happens like that. I think it'll disturb the vibration or something and the thing breaks. Like an opera singer who cracks glass. Google it

This post has been edited by pllx: Sep 29 2009, 09:32 PM

Erm, natural frequency is the frequency of which when applied to an oscillating object, it will oscillate at its maximum 'swing' i.e. maximum displacement.

try not to confuse forced oscillation, which is when u exert external force onto the oscillating system (which may displace it more than the maximum displacement via natural frequency)

anyway, needs verification.. basing of what i've learnt, for like >5 years ago?

can anyone tell me what is quantum mechanic actually?cut the jargons.
tell in common words so layman also can understand.tq.

XD the term mechanics itself is rather difficult to understand ady.

Google helps



Mechanics pertains to the understanding of how things work. At least by definition.

This post has been edited by ZeratoS: Oct 5 2009, 02:49 AM

quantum = atomic/subatomic level
mechanics = mechanism study, like how thing work, why thing won't work

quantum mechanics, in layman explaination, is the study of the behaviour of mass, at atomic/sub-atomic level. It study the behaviour under various condition, configuration, external disturbance, energy level, etc....

It's like study of car behaviour, different engine, different chassis, different fuel, different tire, suspension, and when accelerating uphill, downhill, taking a corner, collision (accident) etc... but everything at atomic/sub-atomic level.