Physics, Chemistry and Biology: Post your doubts here!

[za Shadow]

ok...its quite simple.

for 1 d ii)
the speed that u used was 0.6..correct?
now that speed is actually its maximum speed so it won't be travelling at that speed for the whole 1.2 sec.
thus u divide by 2 to get an average speed = 0.3.
then multiplying 0.3 and 1.2 give 0.36.

for 5 c )
the specific latent heat of fusion is found by how much ice was melted by the heater.
so in order to do that u must know hw much ice was melted by the surroundings.
that amount is given as 2.1...which is the amount which was melted by the surroundings, after the heater was off.
hence even while the heater was on 2.1 g of ice would have been melted by the surroundings.
thus u hv to subtract 2.1 from 16.3, to find out how much ice was melted by the heater.
and since u only hv to find the amount of ice melted by the heater the time is 2min.
hope i helped!!!!

one more thing how did u know its the maximum speed the question didn't mention anythinh about maximum speed??????? and what will the question say so that i know whether to divide by 2 or just use that speed????????

 

[ZainH]

ALWAYS KEEP THE ANGLE IN RARER MEDIUM IN NUMERATOR AND THE DENSER MEDIUM IN DENOMINATOR .....IF THE LIGHT IS TRAVELLING FROM GLASS TO AIR THIS MEANS ANGLE OF INCIDENCE IS IN GLASS AND ANGLE OF REFRACTION IS IN AIR SO FOLLOWING THE RULE IT WILL BE SIN R /SIN I

n
it depends ,,if the refractive index of medium is given then its sin in air / sin in medium
and if ref index of air is given then sin in medium / sin in air ....its better if u learn in this way instead of i and r

THAT IS WHAT OUR TEACHER TOLD US

Thanks for the replies guys, this helped! x)

 

[kboss]

but there is no magnetic field

i think there may be from the thick wire.

 

[za Shadow]

I have my own questions for once.
a) How do you calibrate a CRO?
b) How was the change in velocity found in question 2)c)ii) of the attached past papers?

a) i actually don't know
b) velocity is the 17.5 because u add up all the spped untill the point asked so 10m/s + 7.5m/s and that give 17.5 m/s

hope i helped )

 

[thats_me]

Thanks for the replies guys, this helped! x)

np

 

[kboss]

I have my own questions for once.
a) How do you calibrate a CRO?
b) How was the change in velocity found in question 2)c)ii) of the attached past papers?

section b
add 9.5 and 8
u'll get 17.5 which is the answer.

 

[za Shadow]

i think there may be from the thick wire.

but that doesn't make sense i still can't get the correct answer

 

[ZainH]

section b
add 9.5 and 8
u'll get 17.5 which is the answer.

Would that be the change in velocity?
Pretty sure you'd have to subtract the two values for the "CHANGE"
That's what I think atleast. 1.5m/s should be the answer

 

[kboss]

one more thing how did u know its the maximum speed the question didn't mention anythinh about maximum speed??????? and what will the question say so that i know whether to divide by 2 or just use that speed????????

it says that the trolley reached the speed of 0.6 after 1.2 secs.
so it has to be the maximum speed since it didn't slow down be4 that.

 

[kboss]

Would that be the change in velocity?
Pretty sure you'd have to subtract the two values for the "CHANGE"
That's what I think atleast. 1.5m/s should be the answer

thats for the change in speed.

 

[ThatReallyReallyWeirdDude]

Would that be the change in velocity?
Pretty sure you'd have to subtract the two values for the "CHANGE"
That's what I think atleast. 1.5m/s should be the answer

That's what I want. The change in velocity. Why is 17.5 the change in velocity/ why do you add the 9.5 to the 8?
Change in speed is easy; 9.5-8=1.5m/s
EDIT: I'm an idiot, I get it now. P: The 9.5m/s and 8m/s were in different directions, so it's like 9.5 and -8, it changes by 17.5

 

[ZainH]

That's what I want. The change in velocity. Why is 17.5 the change in velocity/ why do you add the 9.5 to the 8?
Change in speed is easy; 9.5-8=1.5m/s
EDIT: I'm an idiot, I get it now. P: The 9.5m/s and 8m/s were in different directions, so it's like 9.5 and -8, it changes by 17.5

LOL.. god I feel retarded.
Gonna take a break :S

 

[ThatReallyReallyWeirdDude]

guyz mj 11 31 2c ..? :S http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_31.pdf

Okay the work done/energy required for each rung is
forcexdistance = 800x0.3 (cause it has to be meters, so 30cm=0.3m)
=240J
He climbs 20 rungs
so total energy required = 20x240=4800
However he is only 15% efficient, so 4800J is only 15 PERCENT of the amount he uses
so 15% times X = 4800
X = 32000J = 32 kJ
Edit: Since efficiency = useful work output / total energy input, you can use that:
useful work output = 4800J
and efficiency = 15%
so useful/total = 0.15
4800/total = 0.15
total = 4800/0.15 = 32000J

 

[*MK*skydiver :D]

Link to the past paper please. There's three variants so...

Whoops ...my bad ! :/

the link is ::
http://www.mediafire.com/view/?m8bwzxmq6uhg3em ( question 10 is on page 14 )

 

[ThatReallyReallyWeirdDude]

Whoops ...my bad ! :/
the link is ::
http://www.mediafire.com/view/?m8bwzxmq6uhg3em ( question 10 is on page 14 )

Funnily enough I just explained this to a friend, let me copy it

i) When its light in the dark room, the resistance of the LDR will be low, so R and thus A will have a higher share of voltage and thus be 1 (high)
When it's dark, the resistance of the LDR will be high, so R and A will have a lower share of voltage and thus be 0 (low)
ii)

That's what I think at least, and it agrees with paper mark scheme. Note that it stops at the transistor since the logic gate is off and transistor is too
EDIT: Was that the only thing you had a problem with or is it all of question?

 

[thats_me]

Okay the work done/energy required for each rung is
forcexdistance = 800x0.3 (cause it has to be meters, so 30cm=0.3m)
=240J
He climbs 20 rungs
so total energy required = 20x240=4800
However he is only 15% efficient, so 4800J is only 15 PERCENT of the amount he uses
so 15% times X = 4800
X = 32000J = 32 kJ
Edit: Since efficiency = useful work output / total energy input, you can use that:
useful work output = 4800J
and efficiency = 15%
so useful/total = 0.15
4800/total = 0.15
total = 4800/0.15 = 32000J

THANKYOUU!!

 

[gelato]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s10_qp_32.pdf
7a)i)

 

[thats_me]

Okay the work done/energy required for each rung is
forcexdistance = 800x0.3 (cause it has to be meters, so 30cm=0.3m)
=240J
He climbs 20 rungs
so total energy required = 20x240=4800
However he is only 15% efficient, so 4800J is only 15 PERCENT of the amount he uses
so 15% times X = 4800
X = 32000J = 32 kJ
Edit: Since efficiency = useful work output / total energy input, you can use that:
useful work output = 4800J
and efficiency = 15%
so useful/total = 0.15
4800/total = 0.15
total = 4800/0.15 = 32000J

another doubt : O/N 11 var 32 q7c (i) http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_w11_qp_32.pdf hw do we knw if we hav to use speed of sound or light?

 

[chaotic]

Need help in these question, thank you (explain the way to solve, and if you use any formula please don't use symbols, use their meanings F = force, etc.. thank you!)

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_w11_qp_31.pdf
3b (ii)

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_w11_qp_32.pdf
1c (i)
3 (whole question)
6c

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_w11_qp_33.pdf
3b
5b (ii)

 

[wooowooowoo]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s10_qp_32.pdf
7a)i)

330 m/s