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Author Topic: ALL PHYSICS DOUBTS - POST HERE !!  (Read 238206 times)

Offline Ghost Of Highbury

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #870 on: May 21, 2010, 03:23:29 pm »
Quote from: Kimo Jesus on May 21, 2010, 01:48:13 pm
oki doki thanks man ! i understood it ..my concept was wrogn but i used to goet right asnwers for some reason .. now that i understand it <3 cheers + rep !

It was written by cooldude, as i said. Part of the thanks goes to him. Glad the latter explanation helped too :P
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Offline ambitious94

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #871 on: May 21, 2010, 03:59:03 pm »
new doubts...;)
Both questions r from Nov 2008:
1) Q5(c) Using a 40W heater, 16.3g of ice is melted in 2 minutes. The heater is then switched off. In a further 2 minutes, 2.1g of ice is melted.
Calculate the value of specific latent heat of fusion of ice from these results.

2) Q6(b) What's the formula for the refractive index? sinr/sini or sini/sinr? Which is the incident and refracted ray? :S
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holtadit

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #872 on: May 21, 2010, 04:12:41 pm »
Quote from: ambitious94 on May 21, 2010, 03:59:03 pm
new doubts...;)
Both questions r from Nov 2008:
1) Q5(c) Using a 40W heater, 16.3g of ice is melted in 2 minutes. The heater is then switched off. In a further 2 minutes, 2.1g of ice is melted.
Calculate the value of specific latent heat of fusion of ice from these results.

2) Q6(b) What's the formula for the refractive index? sinr/sini or sini/sinr? Which is the incident and refracted ray? :S


COnfused with the same question.... Why do you do 16.3 - 2.1 ???
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Offline Vin

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #873 on: May 21, 2010, 04:21:03 pm »
Q = mL

power is nothing but Joules per second

heat (Q) = 40 J/sec * 120 sec

Q = 4800 J
mass = 16.3-2.1 = 14.2
as the mass melted by the heater is only till 2.1g

4800 = 14.2 * L
L= 338 J/g

lemme check the other ques

ALWAYS formula for refractive index depends from which medium it passes
eg .
From denser to rarer (glass to air) = sin r /sin i
From rarer to denser (air to glass =  sin i / sin r

here its(glass to air) = sin r /sin i

sin r/sin 30 = 1.49
sin r = sin (30) * 1.49
r = sin-1(0.745)
=48.2 o
« Last Edit: May 21, 2010, 04:26:51 pm by ~VIN1094~ »
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Offline Ghost Of Highbury

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #874 on: May 21, 2010, 04:21:30 pm »
Quote from: Ari Ben Canaan on May 21, 2010, 04:12:41 pm
COnfused with the same question.... Why do you do 16.3 - 2.1 ???

"see the question in a different way/manner.... u see  16.3 is not lost by the heater only... they gave u a hint tht excess heat (not from the heater ) was also applied to the ice..

what u need to do, is to take out tht excess heat (by subtracting) and u get the actuall heat supplied by the heater (which is needed for the equation)"

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Offline J.Darren

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #875 on: May 21, 2010, 04:28:34 pm »
Quote from: ambitious94 on May 21, 2010, 03:59:03 pm
new doubts...;)
Both questions r from Nov 2008:
1) Q5(c) Using a 40W heater, 16.3g of ice is melted in 2 minutes. The heater is then switched off. In a further 2 minutes, 2.1g of ice is melted.
Calculate the value of specific latent heat of fusion of ice from these results.

2) Q6(b) What's the formula for the refractive index? sinr/sini or sini/sinr? Which is the incident and refracted ray? :S

heat is gained from the surroundings in the experiment, by measuring for another two minutes, you can work out the effect of heat gained from the surroundings (ice that were melted due to those heat), subtract that from the total amount of ice melted will get you the full amount of ice melted due to the energy supplied by the heater.

Specific latent heat of fusion = ML

40 x 120 = (16.3 - 2.1) L

L = 338 J / g

n = sin i / sin r (from rarer to denser medium. if it is from denser to rarer medium, such as glass to air, then take the reciprocal, sin r / sin i)
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Offline Ghost Of Highbury

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #876 on: May 21, 2010, 04:30:20 pm »
Quote from: J.Darren on May 21, 2010, 04:28:34 pm
heat is gained from the surroundings in the experiment, by measuring for another two minutes, you can work out the effect of heat gained from the surroundings (ice that were melted due to those heat), subtract that from the total amount of ice melted will get you the full amount of ice melted due to the energy supplied by the heater.

Specific latent heat of fusion = ML

40 x 120 = (16.3 - 2.1) L

L = 338 J / g

n = sin i / sin r (from rarer to denser medium. if it is from denser to rarer medium, such as glass to air, then take the reciprocal, sin r / sin i)

yes, thats correct.

another thing to remember , is that the refractive index cannot be less than 1...so if u get a value less than 1, reverse the formula..
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Offline key04

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #877 on: May 21, 2010, 04:34:14 pm »
Hi everyone!!!!!!!!!!!!
how was the exams???
i hope it was good.........
does anyone know any good website 4 bio,chem n phy notes???
i do need it...........
plz tell me......

 Thanks in advance
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Offline WARRIOR

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #878 on: May 21, 2010, 04:36:02 pm »
Quote from: A@di on May 21, 2010, 04:30:20 pm
yes, thats correct.

another thing to remember , is that the refractive index cannot be less than 1...so if u get a value less than 1, reverse the formula..
it depends if ur calculatin the angle of refraction/incidenc in a less dense medium its less than one
                       """""""""""""""""""""""""""""""""""""""""""""""""""in a more dece medium its more than one

but when its for exaplm : calculate the refrative index from speeds.  SPEED OF LIGHT IN AIR/ SPEED OF LIGHHT IN MEDIUM its always above 1
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Offline WARRIOR

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #879 on: May 21, 2010, 04:44:12 pm »
hmm confusion

http://www.freeexampapers.us/IGCSE/Physics/CIE/2003%20Nov/0625_w03_qp_3.pdf

question  11 (a) part 2

With flemmings L.H.R ..the wire moves up.. so beta particles should move the opposite way shouldnt it?
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Offline J.Darren

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #880 on: May 21, 2010, 05:07:56 pm »
Quote from: Kimo Jesus on May 21, 2010, 04:44:12 pm
hmm confusion

http://www.freeexampapers.us/IGCSE/Physics/CIE/2003%20Nov/0625_w03_qp_3.pdf

question  11 (a) part 2

With flemmings L.H.R ..the wire moves up.. so beta particles should move the opposite way shouldnt it?
It goes into the page ... Take a look at the final question of June 06.
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Offline WARRIOR

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #881 on: May 21, 2010, 05:21:11 pm »
Quote from: J.Darren on May 21, 2010, 05:07:56 pm
It goes into the page ... Take a look at the final question of June 06.
look at mark scheme :O

it says moves at smooth curve 90* to the magnetic field  out of the page!

http://www.freeexampapers.us/IGCSE/Physics/CIE/2003%20Nov/0625_w03_ms_1+2+3+5+6.pdf

13th page
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Offline J.Darren

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #882 on: May 21, 2010, 05:27:49 pm »
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Offline WARRIOR

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #883 on: May 21, 2010, 05:31:16 pm »
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Offline J.Darren

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #884 on: May 21, 2010, 05:46:10 pm »
Quote from: Kimo Jesus on May 21, 2010, 05:31:16 pm
THAT MEANS THERE IS A MISTAKE RIGHT  :o :o :o :o :o :o :o :o :o :o :o :o
 not my mistke cool
I do apologise. Clearly I have misread the question (November 03), I thought they are referring to a beam of alpha particle instead of beta particle :(
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