Biology; Chemistry; Physics: Post your doubts here!

[convent2012]

a pendulum oscillates b/w extreme positions X and Z . IT TAKES 0.4 SECONDS TO GO FROM X TO Y , THE MIDPOINT . ( Y is mean position)
WHAT IS THE PERIOD OF THE PENDULUM ?????
A 0.8sec B 1.2sec C 1.6sec D 2.O sec

 

[ashiqbal]

i want help in 5090​

s11 qp12 q7 ​

s10 qp11 q4, q16, q24​

w09 qp1 q16, q14, q9​

s09 qp1 q5, q17, q19​

s11 qp12​

, q7 it would be A as all other sources would have been used up by plant itself, and only the cellulose part remains in large amount​

s10 qp11 ​

, q4(C) boiling denatures enzymes so result is large amount without boiling and traces after boiling so option 4 and 5​

, q16(C) when person starts to exhale, initially volume decreases and pressure increases, until the air flows out and pressure returns to normal after exhalation, similarly when a person inhales, volume increases;pressure decreases until inflow of air cause pressure to return to normal​

, q24(A) you can see that if you try to move your hand in the way it is shown, you will feel biceps contracting and triceps relaxing​

 

[ashiqbal]

a pendulum oscillates b/w extreme positions X and Z . IT TAKES 0.4 SECONDS TO GO FROM X TO Y , THE MIDPOINT . ( Y is mean position)
WHAT IS THE PERIOD OF THE PENDULUM ?????
A 0.8sec B 1.2sec C 1.6sec D 2.O sec

(C) 1.6

 

[Ahmedfj]

Mcq no 13 .firstcalculate moles if Iodine
2.54/254=0.01
Thn by the formula moles = concentration multiplied by volume ,divide 0.01 by 250 and to convert into dm cube,multiply answer by 1000 so the answer will be 0.04 mol/dm cube

Mcq no 19
Magnesium will have the fastest reaction with hcl bcuz it is higher in the reactivity series and more hydrogen bubbles will be produced and zinc is lower in the reactivity series thus it will produce least bubbles of hydrogen gas

Mcq no 24
This will also be done by the same formula
First take out moles of of hcl by multipying concentration by volume .
30 (multiply) 2= 60
Now as the reaction equation says tht 1 mol of hcl reacts with 1mol of naoh thn divide 60 by volume of naoh at highest point i.e 20 .the answer will be 3.

thanx a lot and pls also explain MCQ 35

 

[convent2012]

(C) 1.6

how ??

 

[convent2012]

in dry cell battery energy is converted from chemical ----->electrical ????
in light emission diode energy is converted from light ----> electrical ????
in microphone from sound -----> electrical ????
and what's conversion of energy in photo-emissive cell . please confirm above to me !

 

[ashiqbal]

how ??

period is time for one complete oscillation, which is one complete swing and return back to its original position,X. so if it takes 0.4 sec for X to Y, it will take 0.8 sec for X to Z and 1.6 sec for X to Z and back to X again!

 

[Mayedah]

thanx a lot and pls also explain MCQ 35

Mcq 35
Answer will be c .(3)
Minerals alts ,phosphates and nitrates are used in lakes so they cause eutrofication .!

 

[Tharindu]

How to answer question no. 2 paper 1 (variant 11 ) october november 2011 chemistry

 

[GetSomeLife]

How to answer question no. 2 paper 1 (variant 11 ) october november 2011

Which subject?

 

[ayeshaK]

http://www.xtremepapers.com/papers/...onal O Level/Biology (5090)/5090_s06_qp_2.pdf
Can anybody help with Q5 part (b)

 

[ayeshaK]

And also
http://www.xtremepapers.com/papers/...onal O Level/Biology (5090)/5090_s08_qp_1.pdf
Mcq 38 !!

 

[convent2012]

http://www.xtremepapers.com/papers/CIE/Cambridge International O Level/Biology (5090)/5090_s06_qp_2.pdf
Can anybody help with Q5 part (b)

q5 b i) red is dominant because it appear in f1 generation . cross W will produce same results as in 5.1 because both of them are heterozygous (Tt)

 

[stareaj]

Someone pls tell me how to calculate half life plssssss exampl question 39 oct 09 physic mcq

 

[multixamza01]

Someone pls tell me how to calculate half life plssssss exampl question 39 oct 09 physic mcq

Half life formula :
(count rate specific time) / (count rate at the beginning) = (1/2)^n

n = no. of half-lifes passed .

 

[ashiqbal]

Someone pls tell me how to calculate half life plssssss exampl question 39 oct 09 physic mcq

for a simpler method, halve the count rate, and see how much time it took for the count rate to decrease to half

 

[ashiqbal]

in dry cell battery energy is converted from chemical ----->electrical ????
in light emission diode energy is converted from light ----> electrical ????
in microphone from sound -----> electrical ????
and what's conversion of energy in photo-emissive cell . please confirm above to me !

seriously , are these even included in o level syllabus??!!

 

[ayeshaK]

q5 b i) red is dominant because it appear in f1 generation . cross W will produce same results as in 5.1 because both of them are heterozygous (Tt)

Thankyou !

 

[Tharindu]

Which subject?

Opz...forgot to mention...chemistry

 

[GetSomeLife]

How to answer question no. 2 paper 1 (variant 11 ) october november 2011 chemistry

The student was provided with a thermometer, a stopwatch and a beaker.

Stopwatch can be used to note the TIME
Thermometer can be used to get a reading of the TEMPERATURE
While the beaker is good for nothing

A consists of "Mass" and "Volume"
B consists of "Mass" and "Temperature"
C consists of "Volume" and "Time"
D consists of "Temperature" and "Time" and so is the right answer (as we can only measure the TIME and TEMPERATURE accurately)