E-StoreHome » Ask & Discuss » Physics. » Mechanics « Back to Discussion
Mechanics
16 Dec 2007 19:57:07 IST
0 People liked this
9
608
hey here is are two serious doubts
None
hey fellows here are two serious doubts!!! 1.) supposing i have 2 springs with the same natural length and the same spring constant. i compress one with (a work of say x j)a thread to keep it in a compressed position. i dissolve both in acid with the same number of molecules. both the springs dissolve. will the energy in the two test tubes be different? explain elaborately! 2.) if temperature is the measure of average kinetic energy, then this implies that it is frame dependent. this means that if i go with the same velocity as the molecules, does this mean that their temperature is 0 kelvin? explain elaborately! desperately waitin for a r
Comments (9)
Indzee ...
Hot goIITian
Joined: 2 Dec 2007
Posts: 124
16 Dec 2007 22:10:40 IST
Like
1 people liked this
Dude,
Ans. 1
Energy in both the test tubes will remain same, as both the springs are of same length and same spring constants. There is nothing to explain so elaborately. Here, the compression of spring cannot be taken into picture because the energy of the acid only depends upon the volume and the type of substance dissolved. The only change you will see is that the compressed spring will take more time to dissolve.
It is like dissolving one crystal of sugar in one test tube and one crushed crystal of sugar in another.
Reply
17 Dec 2007 17:59:07 IST
Like
0 people liked this
this has kinda confused me more
well what i thought is, if u do some x J in compressing the spring, there will be a change in potential energy of the molecules of the spring. all the molecules try to come back to equilibrium positions and so when dissolved, the kinetic energy of the molecules of the compressed spring would be higher. the difference in k.e of the two tubes would correspond to x joules (conservation of energy). please tell me what is wrong with this theory
"Energy in both the test tubes will remain same, as both the springs are of same length and same spring constants."
could you explain to me how does this depend on spring constants?
"the energy of the acid only depends upon the volume and the type of substance dissolved. The only change you will see is that the compressed spring will take more time to dissolve.
It is like dissolving one crystal of sugar in one test tube and one crushed crystal of sugar in another. "
well this part is in complete disagreement with my theory. but i have a few nagging doubts.
1.) how can it be said that it depends on volume? if the volume changes, does it change the energy of the acid?
2.) this is in connection to ur sugar example. if the spring was complettely compressed parts of spring would overlap and this would reduce surface area. but it is not given that it is completely compressed, ie surface area does not reduce. how then would the acid molecules be less vigorous in their attack? the rate of dissolution must be the same, right?
the thing is, in ur example of sugar and crushed sugar, there is a difference in surface area and that decides the time factor. i dont think it works here though.
17 Dec 2007 18:18:22 IST
Like
0 people liked this
ans1) the compressed spring will dissolve a bit faster.. but final energy of both solutions will be same.
ans2) kinetic energy isnt frame dependent....
if temperature is the measure of average kinetic energy, then this implies that it is frame dependent .....can u elaborate?
ans2) kinetic energy isnt frame dependent....
if temperature is the measure of average kinetic energy, then this implies that it is frame dependent .....can u elaborate?
17 Dec 2007 18:27:38 IST
Like
0 people liked this
please explain how you get that the compressed spring dissolves faster.
2. the kinetic energy of a body is frame dependent. seen from different frames, it varies.
eg.
if a body seen from ground frame has a velocity v0 and mass m, its kinetic energy wrt ground frame is [m(vo)^2 ]/2. but consider a frame moving with velocity v0 in the same direction as the body. relative velocity =0 and so the kinetic energy of the body as viewed from this frame is 0
17 Dec 2007 18:31:55 IST
Like
0 people liked this
compressed spring will have some work done on it to be compressed while the other is not.. but since the material is same the end energy (finally) will be same... but the rate in the case of compressed spring will be faster because we have done work on it and energy is conserved.
17 Dec 2007 21:20:01 IST
Like
0 people liked this
if the material is the same, how is the end energy the same?
well i'll tell you what - just tell me is my theory is correct, and if wrong, why
you do some work on the spring to compress it, say x joules. then you tie a thread to keep it in the same position. you dip both the springs in the acid.
so basically, the potential energy by virtue of position of compressed spring is more. since the attack of acid molecules on both spring is the same, rate of dissolution is the same
once dissolved, as the potential energy of the compressed spring was more, the kinetic energy of those molecules will be more in comparison to non compressed spring molecules
the difference in kinetic energy will correspond to x joules by conservation of energy
so the heat evolved in the tube with the compressed spring is more
tell me whats wrong with this one
15 Jan 2009 12:38:37 IST
Like
0 people liked this
i agree wid u "tka"
u see when we od work xJ on the spring and tie it with a spring, the work is stored in the spring as potential energy. now when the spring is dissolved by the acid, this PE is manifested in the form of KE which will be gained by the molecules of acid and the sysytem of compressed spring gets heated as compared to the non-compressed one.
i find it to fine agreement to conservation of energy.
Anyone else plz let me know if we are correct???
u see when we od work xJ on the spring and tie it with a spring, the work is stored in the spring as potential energy. now when the spring is dissolved by the acid, this PE is manifested in the form of KE which will be gained by the molecules of acid and the sysytem of compressed spring gets heated as compared to the non-compressed one.
i find it to fine agreement to conservation of energy.
Anyone else plz let me know if we are correct???
Free Sign Up!
Preparing for IIT-JEE ?
Arihant Revision Package for IIT JEE - Books, Practice Tests + Rank Predictor
@ INR 1,995/-
For Quick Info
Find Posts by Topics
Physics.
Topics
9129
19729
3590
2097
7393
2756
2568
Mathematics.
Chemistry.
Biology
Institutes
Parents
Board
Fun Zone
|
|
|
|
|
| 35,229,755 Engineering Questions Attempted |
6,69,530 Visitors Monthly |
79 Engg. Exam Covered |
554 Students Currently Online |
Connect with Us  |
 |
Vriti Communities
Privacy Policy © Vriti 2011