Length contraction??? (1 Viewer)

[matty fwd]

It's funny how intense this debate is getting. It's even funnier that the ppl who wrote this exam would have never even thought about it in the detail that some of these students are. I put 0.3 - but I can see the .19 logic....however I wouldn't put it past them to mark it incorrectly.

 

[yorky]

ok... we are not measuring the length of the electron. We are measuring the a length which the electron observes. This length is not moving, which means the stationary labartory would not see it contract. So the answer is 0.3

I am 100% sure it is 0.3!! even if you just think about it empirically. 0.3 is a much cleaner answer than some shitty decimal 0.192. 0.192 is wrong under all circumstances

just because you dont have the brain capacity to work to 3dp, it was a correct decimal by the way .1920000000, to whatever, if u want to use the shitty analgy, the lenght between anode and cathode cant be measured to decrease by the electron, the electron itslef contracts every dickhed hear can agree with that, by that logic the distance to the electron will appear to be longer than the actual length, because it is relatively smaller within the length, + theory of relativity give it up guys its .192 and u cant get above 99%

 

[hamzah]

OK, PEOPLE. in the electrons frame of reference, the anode appears to travelling toward it at 0.6c, so to the electron the the length infront of it appears contracted. But to the outside observers the lenngth seems the normal lenght which is bigger, hence 0.3m.

There is so much evidence for this i cant beleive you guys can say otherwise.

Like particle accelerators, sub-atomic particles were accelerated to circle a track at about .8c thats really long. Not taking length contraction into account, the scientists caclulated the particle would do like 100 circuits before colliding with itself and reacting (to annhilate itself). They found it did like 800 circuits cos the lenght to the particles seemed much smaller (LENGHT CONTRACTION).

Ok, how about the sylabbus point on the effect of length contraction for space travel. I mean didnt you all say its a good thing, cos to the astronauts on the spaceship the lenght infront of them appears lenght contracted, so they get there quicker, while from earth the length seems the same. (ofcourse this works in conjuction)

I mean seriously you guys are way off....theres all thse other examples which i really cant be screwd writing about cos i know i got the right answer 0.3m 100%. Ask your teachers.

 

[hamzah]

And who said the electron is not a inertial frame of reference, UH dude the Q said it was traveling at 0.6c, THATS A CONSTANT VELOCITY anode or not.

 

[Aznduud3]

the question says:
the distance between the anode and the screen, as measured by the electron's frame of reference, is 0.24

this is exactly the same as a a guy in a spaceship traveling at 0.6c. obviously in HIS frame of reference, ALL laws of physics are true. that is. since he is moving at constant velocity, then its the same as he is stationary. hence, then he would measure the length of the spaceship as the same as it originaly is.

the Laboratory frame of reference is the same as the observer looking at the spaceship. basically the length is going to contract


im assuming for the previous question (mass dilation) you would have got a heaver weight. IF U DID, U ARE CONTRADICTING URSELF.

both questions ask for the same thing - calculating for the same laboratory frame of referece.

and my point is......the answer is smaller than 0.24.

of course, its a trick question though. had me thinking

 

[ze.outlaw]

Yea I got 0.3m too! And I am fairly certain this is correct because 0.24m was the distance between the anode and the deflection plates relative to the electron which was moving at 0.6c which mean 0.24m was Lv and we had to find Lo... wooo

 

[matty fwd]

the question says:
the distance between the anode and the screen, as measured by the electron's frame of reference, is 0.24

this is exactly the same as a a guy in a spaceship traveling at 0.6c. obviously in HIS frame of reference, ALL laws of physics are true. that is. since he is moving at constant velocity, then its the same as he is stationary. hence, then he would measure the length of the spaceship as the same as it originaly is.

fuck......it's 0.19.....but i'm still hoping they might mark it wrong and give 0.3 correct

 

[dunno04]

fuck......it's 0.19.....but i'm still hoping they might mark it wrong and give 0.3 correct

yeh it is 0.192

But u never kno.
WE might be wrong

BUT i'm pretty sure it is 0.192.

 

[icy_meteor]

mmmm , it a tricky question but i think that if its measured from the electrons frame of reference then that will be the rest frame. this has got nothing to do with the tube. just imagine another electron travelling at speed of 0.6 measures the length for the electron and the length is 0.24, however a person from lab's frame of reference sees that the length is contracting coz electron is moving at 0.6

therefore its 0.192 m?

0.3m is convincing as well...so

 

[dunno04]

yea....
I THINk...we shud get a teacher and tell us the answer...

So that we are not convinced by any other answer from STUDENTs.
Everyone want to get it right...

AND FUCK yea!
(I love this...WE can swear in forum...yay!)
hahaha
=D

 

[bboyelement]

the question says:
the distance between the anode and the screen, as measured by the electron's frame of reference, is 0.24

this is exactly the same as a a guy in a spaceship traveling at 0.6c. obviously in HIS frame of reference, ALL laws of physics are true. that is. since he is moving at constant velocity, then its the same as he is stationaryhence, then he would measure the length of the spaceship as the same as it originaly is.

the Laboratory frame of reference is the same as the observer looking at the spaceship. basically the length is going to contract


im assuming for the previous question (mass dilation) you would have got a heaver weight. IF U DID, U ARE CONTRADICTING URSELF.

both questions ask for the same thing - calculating for the same laboratory frame of referece.

and my point is......the answer is smaller than 0.24.

of course, its a trick question though. had me thinking

omg... anode to cathode is not part of his space ship ... the only part of this supposed space ship would be the length of the electron ... if they had said the length of the electron was 0.24 m then yes from the lab's point of view the electron would be 0.192m but it says the length of the anode to cathode which is out side the electron. so its like a space ship travelling one point to another. geez ... its not the proper length god how hard is it to understand... you guys are stoned

 

[shsshs]

FFS 7 page thread on ONE question wTF?

the answer is 0.3m

for the dot point that says 'discuss the implications of length contraction etc. for space travel'

length contraction is an advantage coz the SPACESHIP has to travel through LESS SPACE.

if ur STATIONARY relative to an object, u view its normal length.

if ur MOVING relative to an object, it appears SHORTER; and to the object, YOU APPEAR SHORTER ALSO
i.e. "both see the other as shorter!!" << THIS IS THE IMPORTANT PART

the relative stationary frame always sees the longest length.

and why r sum ppl saying the electron isnt a inertial frame of reference?
its moving at 0.6c. that is a CONSTANT speed ie. non-accelerating frame of reference

ANSWER: 0.3m

 

[yankyfly]

ok ok ok...

The reason why the 0.3 poeple are so much more definite then the 0.192 is because they know they are right. and they are right.

if you put 0.192, just listen to this explanation.

Now... the theory is called length contraction. And the whole point is that objects moving at high speeds relative to you contract.

OK... so we can all accept that length CANNOT EXPAND!! i.e if i was to get a ruler in front of me in my frame of reference, and measure it at 30cm, NO ONE can ever measure it at longer than 30cm, that would be impossible.

So essentially if we work backwards from the answer of 0.192, you are proposing that a scientest put a ruler of length 0.192 along the cathode tube, and measured that as the length.

Then. A speeding electron looked at the ruler and suddenly thought the length EXPANDED? so ruler was moving at 0.6 c and the electron saw it get longer? that is impossible! The whole point of length contraction is that you can never see the length of objects outside your frame of reference expand.

So in actual fact what happened is the scientest puts a 30 cm ruler in front of him. And the ruler is moving at huge speeds relative to the ruler and the length of the ruler contracts. LENGTH CANNOT EXPAND IT CAN ONLY CONTRACT. SO THE ANSWER HAS TO BE 0.3.

Now just quickly before some deadshit tries to justify 0.192 by using my logic aganist me. This shows you don't understand physics - don't bother you will just look dumb.

 

[myeewyee]

i'm an 0.3 person. im pretty shaky with relativity stuff, however i will put forward one piece of experimental evidence for relativity: muons, entering the earth's atmosphere are able to survive for longer than non-relativistic physics would suggest because the apparent distance that they travel is less than what we perceive them to be travelling.

 

[dunno04]

well...
we all argu so that we are right.

BUT we are not the marker.
U never know
BUt 0.192 is right.
Because it is my answer.
=D

 

[macoboi]

I thought the question was well written due to the usage of 'the laboratorys frame of reference' in both parts. it takes the theory of relativity back to its basics, its all relative

relative to the lab, the electron is travelling at relativistic speeds- mass dilates

relative to the lab, the cathode-anode distance is stationary (i.e relative to the electron, the cathode-anode distance is travelling at relativistic speeds, so the 'true', or stationary, distance contracts to 0.24m)

 

[Will_2005_]

i put 0.192 but left out units coz im a douche, i see what u 0.3 ppl r sayin though

 

[psychopath]

yeh i'm convinced .. it's definately 0.3 ...

my only hope now is that .. since it makes specific mention in the question that the "electron starts from rest" .. the measurement of the distance was taken whilst at rest .. and hence not contracted .. in which case the whole question was a trick and the answer is still 0.24m ... cos the question didnt say when the measurement was taken .. like if it had said "when reachign the screen the electron beleived it had travelled .24m " then yeh .3 is right .. but it said "the electron measures distance as .24" .. it's a long shot .. but there is still hope

 

[SL33pY]

im a 0.3 person... but seriously,, this is getting out of hand,, so many replies for one question... could someone possibly get a response from a teacher?!
or are there any mods in uni browsing this thread that could help us out here?

WE NEED A DEFINITE ANSWER!!

i can see the logic from both sides of the argument... so i am really unsure ><

 

[dunno04]

im a 0.3 person... but seriously,, this is getting out of hand,, so many replies for one question... could someone possibly get a response from a teacher?!
or are there any mods in uni browsing this thread that could help us out here?

WE NEED A DEFINITE ANSWER!!

i can see the logic from both sides of the argument... so i am really unsure ><

That's what i said Previously...so that we are sure what is the answer

Is there any teacher here?
Teacher?