Biology; Chemistry; Physics: Post your doubts here!

[thementor]

Hey! Can anyone please xplain question number 31 & 37 of Physics M/J 2011 paper 12!

Q37. dude question 37 uses a very easy concept of graphs......when it says 0.5Hz it means that 0.5 or half a wave passes in 1 second....nw if you count the boxes, half a wave takes 4 boxes....thus 4 boxes represent 1 second.....since it takes 12 boxes for the spot to leave the screen just divide....12/4 =3 seconds....Easy peezy...
the answer is thus A.

Q31. In the case that the switch is OPEN as already shown in the diagram, the current will pass through both the 3 ohm resistors......Find the combined resistance of the two resistors that is it is equal to 3+3=6 ohms (because they are in series). Use V=IR
V=potential difference, R=resistance and I=current.....so I=V/R, I=6 volts/ 6 ohms= 1A so when the switch is OPEN the current is 1A.

Similiarily in the case that it is CLOSED, it will be 2A because now current will pass through only one resistor...
again using V=IR.....I=6V/3ohms= 2A.

so the answer is B.

 

[TheStallion-Reborn]

Q37. dude question 37 uses a very easy concept of graphs......when it says 0.5Hz it means that 0.5 or half a wave passes in 1 second....nw if you count the boxes, half a wave takes 4 boxes....thus 4 boxes represent 1 second.....since it takes 12 boxes for the spot to leave the screen just divide....12/4 =3 seconds....Easy peezy...
the answer is thus A.

Q31. In the case that the switch is OPEN as already shown in the diagram, the current will pass through both the 3 ohm resistors......Find the combined resistance of the two resistors that is it is equal to 3+3=6 ohms (because they are in series). Use V=IR
V=potential difference, R=resistance and I=current.....so I=V/R, I=6 volts/ 6 ohms= 1A so when the switch is OPEN the current is 1A.

Similiarily in the case that it is CLOSED, it will be 2A because now current will pass through only one resistor...
again using V=IR.....I=6V/3ohms= 2A.

so the answer is B.

thnkew so much dude! ^_^

 

[Hasan Asim]

hey what does the answersheet of mcqs look like
because i heard its been changed
for cie science papers

 

[simranlalchand]

The acid G contains two carboxylic acid groups and has the formula
HO2CCxHyCO2H
where x and y are whole numbers.
Deduce the values of x and y in the formula. When te molecular formula of carboxylic acid is 132
[Ar: H, 1; C, 12; O, 16]
it is question from chemistry atp 5070 w12 qp42

 

[Amen]

The acid G contains two carboxylic acid groups and has the formula
HO2CCxHyCO2H
where x and y are whole numbers.
Deduce the values of x and y in the formula. When te molecular formula of carboxylic acid is 132
[Ar: H, 1; C, 12; O, 16]
it is question from chemistry atp 5070 w12 qp42

assume y as x
CxHx+33+24+33=132
12x+x+90=132
x=3.23=3
Cx=12x3=36
36+y+90=132
soy=6
check
HO2CCxHyCO2H
1+16x2+12+12x3+1x6+12+16x2+1=132

 

[robinhoodmustafa]

how to separate chloroplast pigments using chromatography... helppp!!!
Thanks in advance

Use a locating agent on it.

 

[Sparky123]

Any of you people know, about the allowance of 'flexicurves' in the science papers, like it is allowed in maths d?

 

[HarithAslam]

Help plz Bio w12 p11 Q37
I can't figure it out

 

[Sparky123]

Any of you people know, about the allowance of flexicurves in the science papers, like it is allowed in maths d?

?

 

[zohra`xo]

Re: Biology,Chemistry & Physics Help Available Here !



Your question is wrong. Barometer measures liquid pressure. Manometer measures gas pressure. You should learn it. It's confusing , and would cost you later on , so get it straight. Manometer measures gas pressure and barometer measures liquid pressure.

Barometer :
Refer to the book for the diagram. Uses the relation :
Pressure in liquid = Density of liquid x gravitational field strength x height of liquid coloumn.

So in other words if any one of the the three varies , the liquid pressure would vary accordingly. For example if a denser liquid is used , the pressure will increase. If the length is increased the pressure increases. But the gravitational field strength will not change as it is the same everywhere on the planet , but if it were to change , yes the pressure would increase.


Manometer :
Refer to book for diagram. ( it is advised you keep the diagram with you while reading this)
Now as you can see a manometer is a U shaped tube. If you pour liquid into it , the liquid levels reach the same height of both sides. Now to measure the gas pressure , you attach a gas supply to one end. If the gas pressure is more then atmospheric pressure ,then the liquid level will fall in the attached tube. Accordingly the level will rise in the other tube. The level that falls and the level that rises are equal. i.e if the level that has fallen is 2 cm , then the level that rose is also 2 cm. The gas pressure is calculated by adding both levels.

Pressure of gas = Level of liquid that falls + Level of liquid that rises.


Hope this helped.

Hi um, you said a barometer measures liquid pressure, how so? Isn't that wrong? I'm fairly sure a barometer measures atmospheric pressure. It's 76 cm height of mercury at normal atmospheric pressure, and then changes according to height of where we take it.

 

[TheStallion-Reborn]

can any1 please explain the 'displacement-distance' & 'displacement-time' graphs of sound waves? and the terms center of compression and center of rarefaction?

 

[simranlalchand]

assume y as x
CxHx+33+24+33=132
12x+x+90=132
x=3.23=3
Cx=12x3=36
36+y+90=132
soy=6
check
HO2CCxHyCO2H
1+16x2+12+12x3+1x6+12+16x2+1=132

Thanks very much for your help!!

 

[TheStallion-Reborn]

I dont knw if it's the right place to post this question but I didn't find a better place or perhaps I don't have time to look for the right place! So...mi question is, how to correctly check the marking schemes? infront of the appropriate statements it's written A1 or B1 OR C1? wht does that mean??

 

[A star]

can any1 please explain the 'displacement-distance' & 'displacement-time' graphs of sound waves? and the terms center of compression and center of rarefaction?

well its simple displacement time graph can be used to find time period of a wave while displacement distance graph is displacement(a,plitude of a particle) on y axis whilw distance ( showing wavelength on x axis .
adding this is not needed in ur level its As level i guess

 

[faeer2011]

HI all i have a chem problem... Topic: Electrolysis
Q. In an electrolysis experiment same current was passed which deposited 16g of Copper and 6g of Titanium. What is the charge on Titanium ion?
pls reply asap.. Thanks

 

[robinhoodmustafa]

Any of you people know, about the allowance of 'flexicurves' in the science papers, like it is allowed in maths d?

Why do u need a Felxi Curve in Science paper.. The graphs are mostly polygon type of.U just need to join point with a scale

 

[Sparky123]

Why do u need a Felxi Curve in Science paper.. The graphs are mostly polygon type of.U just need to join point with a scale

the past papers are filled with questions that ask us to plot 'curves' especially in paper 'four aka atp'.
like soulubility curves, titration curves etc in chem
like enzyme rate of activity in bio. etc

 

[Hasan Asim]

\Hasan Asim, post: 468969, member: 48531"]hey what does the answersheet of mcqs look like
because i heard its been changed
for cie science papers plz tell

 

[robinhoodmustafa]

the past papers are filled with questions that ask us to plot 'curves' especially in paper 'four aka atp'.
like soulubility curves, titration curves etc in chem
like enzyme rate of activity in bio. etc

Noo. Check Recent year paper. The graph are really simple no curve

 

[Sparky123]

Noo. Check Recent year paper. The graph are really simple no curve

well, curves are there check last questions of chem paper, initials of phy and bio: even in the mark scheme the term curves is used, so why do you thing these are straight lines!?