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Author Topic: ALL PHYSICS DOUBTS - POST HERE !!  (Read 230467 times)

Offline Ivo

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2040 on: May 26, 2010, 04:43:18 pm »
Quote from: Ivo on May 26, 2010, 04:40:36 pm
So is the answer B?

Guys, do you realise this question is different to the "***m"
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Offline thenewkid™

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2041 on: May 26, 2010, 04:44:33 pm »
yes its the same 1
i can even draw the diagram
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Offline Ivo

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2042 on: May 26, 2010, 04:45:38 pm »
Quote from: thenewkid™ on May 26, 2010, 04:44:33 pm
yes its the same 1
i can even draw the diagram

No, this question is about STEEL...
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Offline Raywin

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2043 on: May 26, 2010, 04:46:25 pm »
Hey guys... doubt. O/N 08 Q 5(c) :/ The paper doesnt open for some reason. So heres the Q

Using a 40w heater, 16.3g of ice is melted in 2.0 minutes. The heater is then switched off. In a further 2.0 minutes, 2.1g of ice is melted. Calculate the value of the specific latent heat of fusion of ice from these results.  



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Offline Malak

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2044 on: May 26, 2010, 04:48:29 pm »
Q: draw wavefronts to show what happens after the waves strike the surface

Anyone? thx :D

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Offline ambitious94

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2045 on: May 26, 2010, 04:49:48 pm »
Quote from: thenewkid™ on May 26, 2010, 04:44:33 pm
yes its the same 1
i can even draw the diagram
guys what's all the fuss about. It isnt even the same thing n ur makin it kinda obvious!
The answer is B.
N I solved this question in a pastpaper myself! (Bet u all did XD)  :D
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Offline Ivo

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2046 on: May 26, 2010, 04:51:07 pm »
Quote from: ambitious94 on May 26, 2010, 04:49:48 pm
guys what's all the fuss about. It isnt even the same thing n ur makin it kinda obvious!
The answer is B.
N I solved this question in a pastpaper myself! (Bet u all did XD)  :D

Is it because first time, it attracts.  But when current is reversed, steel is magentically hard so hangs on to magnetism, so it repels, cos if forms poles?
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Offline Shazizzzle

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2047 on: May 26, 2010, 04:56:23 pm »
Quote from: Raywin on May 26, 2010, 04:46:25 pm
Hey guys... doubt. O/N 08 Q 5(c) :/ The paper doesnt open for some reason. So heres the Q

Using a 40w heater, 16.3g of ice is melted in 2.0 minutes. The heater is then switched off. In a further 2.0 minutes, 2.1g of ice is melted. Calculate the value of the specific latent heat of fusion of ice from these results.  





Using the formula for latent heat, P X T = mL, we can find the spc. lt. ht.

Now, 16.3 g was melted USING THE HEATER.
Without the heater, 2.1g of ice melted in the same. That was due to the heat from surroundings!
So, for the mass the heater itself melted= heater - without heater
= 16.3 - 2.1
=14.2

time= 2 min = 60 x 2 = 120 s
Now, p X t = mL
40 X 120 = 14.2 X L
4800/14.2 = L
L= 338.028
thus, L = 338 J/g
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Offline Shazizzzle

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2048 on: May 26, 2010, 04:57:08 pm »
So... What're you guys doing for Paper 3?
We obviously cannot complete the entire syllabus in one day.
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Offline Raywin

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2049 on: May 26, 2010, 04:58:33 pm »
Quote from: Shazizzzle on May 26, 2010, 04:56:23 pm
Using the formula for latent heat, P X T = mL, we can find the spc. lt. ht.

Now, 16.3 g was melted USING THE HEATER.
Without the heater, 2.1g of ice melted in the same. That was due to the heat from surroundings!
So, for the mass the heater itself melted= heater - without heater
= 16.3 - 2.1
=14.2

time= 2 min = 60 x 2 = 120 s
Now, p X t = mL
40 X 120 = 14.2 X L
4800/14.2 = L
L= 338.028
thus, L = 338 J/g

Wait. I thot the Q said that AFT 16.3g of ice is melted the heater is turned off.. so why r we subtracting 2.1 from 16.3?? Thts wht i dont get!! Thx a lot! :)
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Offline Adzel

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2050 on: May 26, 2010, 04:59:54 pm »
Quote from: Shazizzzle on May 26, 2010, 04:57:08 pm
So... What're you guys doing for Paper 3?
We obviously cannot complete the entire syllabus in one day.


Im actually going through my previously solved pastpapers (2009 - 2002) + Reading my text book, how about you?
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Offline MasterMath

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2051 on: May 26, 2010, 05:00:12 pm »
Anyone can help me with Vernier calipers? ive never done it and never even heard about it in school  ??? So anyone can tell me how to use it or anything ?

Thanks!
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holtadit

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2052 on: May 26, 2010, 05:00:26 pm »
Quote from: Shazizzzle on May 26, 2010, 04:57:08 pm
So... What're you guys doing for Paper 3?
We obviously cannot complete the entire syllabus in one day.


REVISION, REVISION and lets see MORE REVISION !! :P
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Offline Malak

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2053 on: May 26, 2010, 05:03:41 pm »
Quote from: ang3l on May 26, 2010, 04:48:29 pm
Q: draw wavefronts to show what happens after the waves strike the surface

Anyone? thx :D


help??
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Offline Shazizzzle

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2054 on: May 26, 2010, 05:03:51 pm »
Quote from: Raywin on May 26, 2010, 04:58:33 pm
Wait. I thot the Q said that AFT 16.3g of ice is melted the heater is turned off.. so why r we subtracting 2.1 from 16.3?? Thts wht i dont get!! Thx a lot! :)

Yeah, well, the heater gave it the activation energy to BEGIN melting!
When the heater stopped, the melting that took place for the next two minutes, was by the heat energy provided by the surroundings.
That heat energy from the surroundings was also provided WITH the heater, so the 16.3 g was a combination of melting due to heater, AND melting due to heat from surroundings.
Therefore, to calculate the mass melted by THE HEATER ITSELF, we subtracting the reading WITHOUT HEATER, from the reading for both. :)
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