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Author Topic: IGCSE PHYSICS  (Read 23612 times)

Offline @d!_†oX!©

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Re: IGCSE PHYSICS
« Reply #90 on: November 07, 2009, 06:30:34 pm »
just to add on nd make it even easier for moon to understand....
see, just remember that to alter the temperature at which the light switches on, u gotta change the resistances as cooldude said...
so there are two resistors in the circuit, nd u can't change the resistance of the thermistor cuz it depends on the temperature only...so to change the voltage at which the transistor switches on, we have to change the resistance of R1....
hope u get it!!!
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Offline cooldude

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Re: IGCSE PHYSICS
« Reply #91 on: November 07, 2009, 06:37:18 pm »
i didnt knw which varaint u were askin for, neway ur ans---

we knw that (p1*v1)=(p2*v2);

therefore 12000*75=300000*v2
therefore v2=30mm
the distance of the piston from the closed end was=75mm
the distance of the piston from the closed end now is=30mm
therefore the distance it has been moved=75-30-45mm
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Offline @d!_†oX!©

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Re: IGCSE PHYSICS
« Reply #92 on: November 07, 2009, 06:37:50 pm »
hey for ur second question:
see
P1*V1=P2*V2
P1=1.2*10^5 Pa
V1=Area*75
P2=3*10^5 Pa
V2=length*Area
because u know the area is same
thus put the values in the formula and find out the length
length=30mm
now, because the piston was 75mm from the closed end and is now 30mm from the closed end, thus the distance moved=75mm - 30mm =40mm
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Offline @d!_†oX!©

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Re: IGCSE PHYSICS
« Reply #93 on: November 07, 2009, 06:38:30 pm »
sorry cooldude...didn't see that u already posted.... ::)
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Offline cooldude

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Re: IGCSE PHYSICS
« Reply #94 on: November 07, 2009, 06:43:15 pm »
Quote from: @d!_†oX!© on November 07, 2009, 06:38:30 pm
sorry cooldude...didn't see that u already posted.... ::)


k np
« Last Edit: November 07, 2009, 06:49:43 pm by cooldude »
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Offline moon

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Re: IGCSE PHYSICS
« Reply #95 on: November 07, 2009, 07:02:25 pm »
Thanx a lot for both of u as u helped me to understand these questions... :) :)
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Offline cooldude

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Re: IGCSE PHYSICS
« Reply #96 on: November 07, 2009, 07:29:58 pm »
Quote from: moon on November 07, 2009, 07:02:25 pm
Thanx a lot for both of u as u helped me to understand these questions... :) :)

np, ur welcum feel free to ask some more qs
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Offline @d!_†oX!©

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Re: IGCSE PHYSICS
« Reply #97 on: November 08, 2009, 04:09:15 am »
Quote from: cooldude on November 07, 2009, 06:37:18 pm
i didnt knw which varaint u were askin for, neway ur ans---

we knw that (p1*v1)=(p2*v2);

therefore 12000*75=300000*v2
therefore v2=30mm
the distance of the piston from the closed end was=75mm
the distance of the piston from the closed end now is=30mm
therefore the distance it has been moved=75-30-45mm
By the way cooldude...ur method is wrong cuz 75mm is not the volume but the length....u gotta show it in the volume format as i did in my post....
just look back cuz if u show this working in ur p3, u will lose some of ur marks there....
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Offline Ghost Of Highbury

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Re: IGCSE PHYSICS
« Reply #98 on: November 08, 2009, 05:40:59 am »
i suppose he cancelled out the area because they were common, and thus had only 75mm
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Offline @d!_†oX!©

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Re: IGCSE PHYSICS
« Reply #99 on: November 08, 2009, 05:52:14 am »
hmmm...maybe because dts wt we ought to do...bt m just telling him dt the cancelling of the area is  necessary to show....
By the way aadi, do u know the formula for the focal length...???
i know for convex lens, just wanna know if it is the same for concave as well...
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Offline Ghost Of Highbury

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Re: IGCSE PHYSICS
« Reply #100 on: November 08, 2009, 05:59:12 am »
i guess its the same

\frac{1}{f} = \frac{1}{so} + \frac{1}{si}

diverging lenses are assigned negative focal lengths.
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Offline @d!_†oX!©

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Re: IGCSE PHYSICS
« Reply #101 on: November 08, 2009, 06:02:31 am »
i thought it was negative So cuz its also on the same side then...
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Offline Ghost Of Highbury

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Re: IGCSE PHYSICS
« Reply #102 on: November 08, 2009, 06:11:04 am »
what?!?!?!

dint i write negative?
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Offline @d!_†oX!©

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Re: IGCSE PHYSICS
« Reply #103 on: November 08, 2009, 06:12:41 am »
u sadi f negative nd m saying So negative....as in the distance of the object from the center...
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Offline HalpPlease

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Re: IGCSE PHYSICS
« Reply #104 on: November 08, 2009, 06:18:08 am »
do we have to know that formula? can anyone expand on it because i am really confused  ??? o_O
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