[ARPAN]

A man is known by his deeds

at the very outset i use this very platform to greet all the existing members to this splendid forum and at the same time begin a discussion into the profound CLASSICAL MECHANICS..

the basic requirements of this discussion will be a course in calculus and an inquisitive mind. the articles will deal into details of Mechanics, yet cater to the beginners with its simplicity...

LET'S GET STARTED....

the entire discussion will be in question- answer format....

1. what is the significance of the equation F= m.a

answer to be provided in the next two days..

[bottomlander]

Originally Posted by ARPAN A man is known by his deeds 1. what is the significance of the equation F= m.a answer to be provided in the next two days..

Some careful physicists clarify that E = mc2 should actually be E = m.c2 .

1) Perhaps better express it as: F= m. a ;
2) a is a vector (directional, with an origin/point of action), so F should be a vector also;
3) only when m is non-zero, then a = zero will make F =0 ;
4) when m or a is uncertain (or below Planck scale), so will F ;
5) when m is zero (any matter entity cannot be of zero mass), F cannot be non-zero, otherwise a will be infinite.

Just my guess. Seems that my proposal is different to your good answer in mind.

Best Regards. Bottomlander

[neutralino]

F=ma is perfectly valid as it stands. It doesn't make much sense to be talking about changes in force, since the reference value will always be zero. That is, zero force gives no acceleration, and thus if one assigns a non-zero force to a body, the acceleration will be non zero.

Of course, the more general form of the equation is ; i.e. the force is equal to the time rate of change of momentum. For normal bodies with constant mass, this reduces to the well known expression of Newton's second law.

Since this thread is discussing physics, it is more suited to the physics forums than the introductions forum and thus I am moving it there. Welcome to the forums, BTW, Arpan.

[ARPAN]

thanks for ur valuable suggestions. in due course of time i will present my views on force and change in momentum concept and Einstein mass energy equivalence..

at present, lets ponder over the validity of F=m.a
as u know , it seems not to hold true in case of non-inertial frame of reference i.e. accelerating frame with respect to earth, so can u propose an extension of this equation..

last time, i asked you about the relevance of F=m.a
remember that this very equation relates almost all forces of nature and the acceleration generated from it. it is, in terms of physics the very definition of force.

gravitational force= gmM/R.R
electrostatic force=kqQ/r.r
and so on.... all forces can be related to it...think!!!

question 2.

this Question may seem out of context but nevertheless it is within the domain of physics
CASE-1
consider a blown balloon. make a hole in it. it will shrink immediately with a possible sound.


CASE-2
now make a hole in the balloon first and then start blowing till it attains a considerable size. secure the balloon at the mouth. u can detect the air inside escaping from the hole but at a much slower rate than in the first case.

now the BIG question WHY IS IT SO ????

[bottomlander]

Originally Posted by ARPAN CASE-1 consider a blown balloon. make a hole in it. it will shrink immediately with a possible sound. CASE-2 now make a hole in the balloon first and then start blowing till it attains a considerable size. secure the balloon at the mouth. u can detect the air inside escaping from the hole but at a much slower rate than in the first case. now the BIG question WHY IS IT SO ????

My guess on the different outcomes between CAse1 and CASE 2 is that:
In CASE 1, the air inside the balloon has no other choice but to burst out due to the quick contraction of the balloon.

In CASE 2, while the size of the hole remains the same, the rate of out going air is affected by 2 factors: the rate of incoming air by your mouth and the contracted volume inside the balloon.
In case the size of the balloon keep equilibrium, the amount of incoming and outgoing air should be the same. That means, it seems to be under control.

To minimize personal perceptions concerning the seriousness of CASE 1, I suggest to mount the balloon under the water tap instead of the mouth.
Then, this test/experiment will have more measurable results.
How far and how quick the water goes out through the hole is more observable/recordable than just with the air from mouth.

It is true that any good idea (like that of ARPAN), will not be presented in full implementations in its first appearance.

Best Regards. Bottomlander

[ARPAN]

u r on ur way, bottomlander.

question 3.
hold a magnet fixed and keep bringing an iron bar towards it.
We observe that the iron bar gets attracted towards the magnet everytime it is kept within a certain range of the magnet... from where does this energy come i.e. who does the work and on whom the work is done...THINK!!

let us assume that this energy is obtained from either the magnet or iron internal energy.. And if this were so then after repeating the experiment for a good number of times the magnet would lose its magnetism or the iron after losing all its energy would no longer be attracted towards the magnet. but in practice neither of the things happen.WHY ????
we know (although without any proof but basically by extensive experiments performed by our scientists) that energy can neither be created nor be destroyed..ALSO THINK ABOUT THE SOURCE OF THE ENERGY BY VIRTUE OF WHICH IRON GETS ATTRACTED....OR ARE WE HEADING TOWARDS CONSTRUCTION OF A PERPETUAL MACHINE...

one common misconception is that the iron might have got magnetised during the course of the experiment. to get a clear picture u can consider taking different pieces of iron bar each time yet arriving at the same result..

u can use the concept of magnetic domains if necessary...

[bottomlander]

Originally Posted by ARPAN u r on ur way, bottomlander. question 3. hold a magnet fixed and keep bringing an iron bar towards it. We observe that the iron bar gets attracted towards the magnet everytime it is kept within a certain range of the magnet... from where does this energy come i.e. who does the work and on whom the work is done...THINK!! let us assume that this energy is obtained from either the magnet or iron internal energy.. And if this were so then after repeating the experiment for a good number of times the magnet would lose its magnetism or the iron after losing all its energy would no longer be attracted towards the magnet. but in practice neither of the things happen.WHY ???? we know (although without any proof but basically by extensive experiments performed by our scientists) that energy can neither be created nor be destroyed..ALSO THINK ABOUT THE SOURCE OF THE ENERGY BY VIRTUE OF WHICH IRON GETS ATTRACTED....OR ARE WE HEADING TOWARDS CONSTRUCTION OF A PERPETUAL MACHINE... one common misconception is that the iron might have got magnetised during the course of the experiment. to get a clear picture u can consider taking different pieces of iron bar each time yet arriving at the same result.. u can use the concept of magnetic domains if necessary...

I am thinking about the contribution from potential energy.
I prefer an analogy of gravitational field rather than an electric field (seems that magnetic fields cannot be shielded).
Static electric field can be shielded with an hollow metallic sphere, but magnetic field can't (only can be neutralized under opposite polarization).

It looks like a PERPETUAL DEVICE only when the additional work of moving out the iron bar (restore the potential energy) hasn't been taken into account.
Work/power is required for the removal of the old iron bar because magnetic field cannot be shielded.

Just a wild guess because I forget much of my knowledge in physics course already.

Best Regards. Bottomlander

[ARPAN]

could u explain the relevance of gravitational field in the above discussion..

now question 4.
have u ever seen the iron-welders doing their job. what u sense is astonishing for it appears (not confirmatory) that the sound from the welding machine reaches our ears before the light (in form of electric sparks) does so... is the statement that light travels faster than sound wrong or is their any other fact.. SUGGEST

question 5.
as calculus is an integral part of physics, i would like to putforth a question on the subject

let F(x)= x^2
then we get its derivative as 2x

the same function can be represented as F(x)=x.x.x.x......... x times
now differentiate the function
u get 1+1+1+1+........ x times = x

although we take the same function we arrive at two different results.
where the fault or is the entire calculus wrong....THINK!!

[ARPAN]

happy to receive answers from bottomlander and neutrilano
any member visiting this site is requested to actively participate in the discussion on general physics and classical mechanics, in particular..
all suggestions for further improvement are welcome..

special message for neutrilano and bottomlander

get ur friends to participate in this site...
members of this discussion have the right to information regrding other members which is to be obtained through REQUESTS...

[neutralino]

Originally Posted by ARPAN let F(x)= x^2 then we get its derivative as 2x the same function can be represented as F(x)=x.x.x.x......... x times

The problem is in your definition here. F(x)=x^2=x.x. Differentiating this, by the product rule, gives dF/dx=1.x+1.x=2x, as above.

The second function you describe is F(x)=x^x.