Physics, Chemistry and Biology: Post your doubts here!

[ktc]

when it says (in paper 6) draw a smooth line graph, does this mean to draw it with the rule? or just draw it smootly without it??

I remember asking the exact same question to my teacher, infact – and according to her, ‘smooth line graph’ doesn’t mean ‘draw a straight line using the ruler’, it means draw free - hand and ‘smoothly' – it could be a ‘smooth curve', too.

 

[princessanum]

I remember asking the exact same question to my teacher, infact – and according to her, ‘smooth line graph’ doesn’t mean ‘draw a straight line using the ruler’, it means draw free - hand and ‘smoothly' – it could be a ‘smooth curve', too.

i agree wd u kfc

 

[hredoymohammad]

how to be sure if any object is perpendicular or paralllel to a bench?
how to arrange a set square either side of a cylinder/sphere to measure diameter?
thx

 

[konye]

it is a metalloi

Q1: H+ ions are attracted to d cathode while OH- ions are attracted to the anode. All the hydrogen is released at the cathode but sum of the OH- ions r used to form water along wid the O2! Therefore, almost double de amount of H2 iz produced dan d amount of O2!
u can see dis frm da eqn:
Cathode:
2H+ + 2e- gives H2
Anode:
4OH- gives 2H2O +O2 + 4e-

Q2: i thinku mistook Aluminium OXIDE for CHLORIDE! cuz den o2 iz released at such a high temperature the carbon anode reacts with the oxygen to form CO2 and escape as gas......thrfor they hav to be replace frequently. i also thinku mistook aluminate for aluminium choride because during the extraction of aluminium which is done by electrolysis of aluminate the anode made up of graphite(carbon macromolecule) burn in presence of oxygen to form carbon di oxide

 

[konye]

I am having problem with moments. Especially stable,neutral and unstable equilibrium..plx help!!!!!!!!!!

for stable equilibrium when an object is displaced it returns back to its original position for neutral equilibrium when it is displaced it maintains its new position

 

[ktc]

how to be sure if any object is perpendicular or paralllel to a bench?
how to arrange a set square either side of a cylinder/sphere to measure diameter?
thx

Perpendicular: by measuring the angle made between the object and the bench; it should be 90 degrees.

Parallel: by measuring the distance between the object and the bench using a ruler. If the distance measured is the same between the object and bench throughout, then we can conclude that the object is parallell to the bench.

Diameter: place 2 set squares on either side of a cylinder/sphere, such that it looks like two right angled triangles placed parallel to one another. Then measure the distance between the two set squares; the distance measured is the diameter of the sphere/cylinder.

 

[Mirna Atef]

i'm asking for the marking scheme of june/nov from 2000 to 2002 for physics 0L

 

[Spirit95]

http://www.xtremepapers.com/CIE/Cambridge IGCSE/0625 - Physics/0625_s02_qp_3.pdf

I need you to explain to me these questions:
Question 5 aii) and b).
Question 8 without the e) part.

 

[allysaleemally]

Hello,

which calculators can be used in IGCSE Maths and Physics.
is this Casio one allowed http://edu.casio.com/products/standard/fx991es/
or do we have to use the basic one: http://edu.casio.com/products/standard/fx85ms/

some people say that u cant use the Fx 991 calculator?

 

[Ahmed Khider]

In w11 qp 32 i didnt know how to solve questions 1,3 & 10...any help? P.s i didnt understand question 3(a) so if any one can explain it it would be appreciated.

 

[Ahmed Khider]

In w11 qp 32 i didnt know how to solve questions 1,3 & 10...any help? P.s i didnt understand question 3(a) so if any one can explain it it would be appreciated.

 

[sea_princess]

Hello,

which calculators can be used in IGCSE Maths and Physics.
is this Casio one allowed http://edu.casio.com/products/standard/fx991es/
or do we have to use the basic one: http://edu.casio.com/products/standard/fx85ms/

some people say that u cant use the Fx 991 calculator?

no I think the fx991 is allowed too, I used it and lots of my friends used it too. and no one said anything

 

[A.H]

no I think the fx991 is allowed too, I used it and lots of my friends used it too. and no one said anything

well what about this one http://edu.casio.com/products/standard/fx82es/ in Biology, Physics, and chemistry IGCSE
And also Maths Edexcel??

 

[sea_princess]

well what about this one http://edu.casio.com/products/standard/fx82es/ in Biology, Physics, and chemistry IGCSE
And also Maths Edexcel??

I believe it's allowed too but I don't know about edexcel
I know about these because these were the calculators we used in our exam

 

[A.H]

I believe it's allowed too but I don't know about edexcel
I know about these because these were the calculators we used in our exam

I just asked yesterday a friend of mine and she said she used it for her Maths Edexcel last June... Thanks for your help though

 

[sea_princess]

I just asked yesterday a friend of mine and she said she used it for her Maths Edexcel last June... Thanks for your help though

you're welcome

 

[namandbone77]

can someone please post notes on electronics and electromagnetism in physics

 

[ktc]

http://www.xtremepapers.com/CIE/Cambridge IGCSE/0625 - Physics/0625_s02_qp_3.pdf

I need you to explain to me these questions:
Question 5 aii) and b).
Question 8 without the e) part.

Question 5]
(a) (ii) Draw an incident ray from P, striking the edge of the plane mirror [including a normal to it], then produce a reflected ray of the same angle, and the reflected ray will strike the display counter at one point. The small part of the display counter after the point where the reflected ray strikes should be shaded – that is the part of the display counter that cannot be seen from P.

(b) 1.5m (approximately)

Question 8]
(a) 240 : 15 = 16
(b) The graph should be half wave rectification.
(c) The diode present in the circuit allows the current to flow in one direction only. The positive half of the Alternating current is passed, the other half is blocked. The diode acts as a rectifier and converts alternating current into direct current.
(d) Draw a battery connected to the circuit. Make sure the polarities are correctly in place.

In w11 qp 32 i didnt know how to solve questions 1,3 & 10...any help? P.s i didnt understand question 3(a) so if any one can explain it it would be appreciated.

Question 1]
(a) Gravitational potential energy = mgh
m = [80/1000] = 0.08kg
g= 10m/s2
h = [2.000 – 1.932] = 0.068m
Thereby, 0.08 x 10 x 0.068
= 0.0544J/Nm.

b) To calculate speed, use ½ m v2
Since kinetic energy = gravitational potential energy,
½ x 0.08 x v2 = 0.0544
Hence, v = 1.2m/s

(c) (i) Actual speed = distance/time
= [2.5÷100] / [22÷1000]
= 1.1m/s
(ii) The difference in the value of the actual speed and calculated speed may be due to air resistance.

Question 3]

a) The difference in the pressure between the top and bottom surface is found by ‘ρgh’
ρ = 1000kg/m3
g = 10N
h= [7/100]m [convert cm to m, to keep it in SI units]
1000 x 10 x 0.07 = 700N/m2

(b) Force = pressure x Area.
= 700Pa x [0.21 x 0.1]m
= 14.7N

c) Acceleration = Force/mass
= [30.9 – 14.7]N / 3.09kg
= 5.24m/s2

Question 10]

a) The resistance decreases.

(b)
(i) At A -> light in the darkroom: High [input 1]
->dark in the darkroom: Low [input 0]
(ii) At B -> Switch in position P: High [input 1]
->Switch in position Q: low [input 0]

(c) AND gate

(d) Transistor

(e) When light strikes the LDR, its resistance falls, therefore input A and B are 1 [high]. The output C is also 1 [high]. The transistor turns on and the buzzer sounds.

 

[AtemisDelta]

sum1 plz tell me how 2 solve chemistry s09/32 q 5
plz help

 

[ktc]

sum1 plz tell me how 2 solve chemistry s09/32 q 5
plz help

Question 5]

(a)
(i) Fe3+ + 3F -> Fe F3

(ii) The mole ratio of Sodium fluoride to Iron (iii) Chloride is 3 : 1, respectively.
Which means, 3 moles of Sodium Fluoride is needed to prepare 1 mole of Iron (iii) Chloride.

(iii) The mixture is washed with distilled water to remove any traces of the soluble impurities of Sodium fluoride.

(iv) To remove the water content from the mixture and dry it.

(b) T3PO4