Biology; Chemistry; Physics: Post your doubts here!

[ashiqbal]

Aluminium sulphate is added to coagulate small particles of clay so that they form larger clumps, which settle more rapidly
I am sure

are u sure they are clay particles !!!

 

[GetSomeLife]

PHYSICS:
Please answer the following question,
Acceleration is also known as or taken as Gravitational Field Strength(or vice versa),
Now if a car moves at constant velocity it Acc is zero,would its G also be zero?
Also a parachute comes down at constant velocity would its G be zero or not?

How did you come to the conclusion that "Acceleration is also known as or taken as Gravitational Field Strength"?
They are 2 different things!

1) g = Acceleration of free fall (10 m/s2)
2) g = Gravitational field strength (10 N/kg)

Now if a car moves at constant velocity it Acc is zero,would its G also be zero?

THIS acceleration and the acceleration of free fall are different. Whereas, the acceleration may be zero here as the resultant force is 0 and mass of the car remains constant, the acceleration of free fall is STILL 10m/s2 but will be ignored in such a question. (there is a little change but you will study that later on)
The gravitational field strength is 10 N/kg!

Also a parachute comes down at constant velocity would its G be zero or not?

No, it will be 10 N/kg as that is the pull of the earth... the same everywhere but reduces as you get away from the earth's center

 

[GetSomeLife]

are u sure they are clay particles !!!

I am pretty sure they can be called 'clay particles'

A sedimentation tank has chemicals known as flocculants, for example aluminium sulphate, added to it to make the smaller particles (which remain in the water as collided clay) stick together to form larger clumps and sink rapidly

 

[SulmanAli]

Only two weeks for exams....anyone has any idea how to revise for physics and chemistry thoroughly...but I want to spend min time possible....

just read the key points of the chapter and do maximum past papers and read examiner reports .

 

[SulmanAli]

Please give the link of physics notes that are working ..Most of the notes that i viewed are corrupted .

 

[Dukeofwin]

to clear your confusion in first part, acc is not the same as gravity. we take acceleration due to force of gravity=10ms-2. and the direction of gravitational force and hence the direction of acc is downward
if a car is moving at constant velocity, its acceleration forward or backward would be zero as there is no resultant force acting on car. however, it is not related to gravity being zero, as there is no resultant force due to gravity(the road pushes the tyre back up), so acceleration downward is also zero, but the gravitational force is continuously acting. and dont confuse acceleration due to gravity with acceleration due to forward force of engine of a car

if a parachute comes down at constant velocity, its acceleration would be zero because the downward force due to gravity is opposed by equal upward force of air resistance. Note that in any case, whether acc is zero or not, there is a gravitational force acting on a body. accceleration is zero only when all forces are balanced(in other words, if there is no resultant force acting on a body)

Thanks alot

 

[Dukeofwin]

How did you come to the conclusion that "Acceleration is also known as or taken as Gravitational Field Strength"?
They are 2 different things!

1) g = Acceleration of free fall (10 m/s2)
2) g = Gravitational field strength (10 N/kg)


THIS acceleration and the acceleration of free fall are different. Whereas, the acceleration may be zero here as the resultant force is 0 and mass of the car remains constant, the acceleration of free fall is STILL 10m/s2 but will be ignored in such a question. (there is a little change but you will study that later on)
The gravitational field strength is 10 N/kg!


No, it will be 10 N/kg as that is the pull of the earth... the same everywhere but reduces as you get away from the earth's center

Thanks as well

 

[multixamza01]

Please give the link of physics notes that are working ..Most of the notes that i viewed are corrupted .

The book is the only notes that aren't ''corrupted''

 

[Ahmedfj]

BIOLOGY

i dont know how to read ventricle graphs (mcq 14 june 2006) and i have seen that there are 4-5 questions concerning these types of graphs in past papers so can anyone pleeeeeeeease explain how to read these graphs ???

 

[fatikhalid]

can any one explain 5090 s05 qp 1 mcq no 40 and 37 and 12??

 

[ashiqbal]

can any one explain 5090 s05 qp 1 mcq no 40 and 37 and 12??

draw genetic cross diagram for both question no 40 and 37.
for 40= D d * d d
Dd Dd dd dd
so 50% chance or 0.5 probability.

for 37= A O * A B
AA AB AO BO
AA and AO are blood group A, BO is blood group B and AB is blood group AB.

for 12=the only reason which fits here is that roots were damaged while transporting, so they cannot take up water fast enough. wilting occurs when the rate of water uptake is less than rate of water loss. the stems were not touched, wilting does not relate to mineral ions, and if leaves lose less water, the cells would become more turgid rather than flaccid!

 

[Ahmedfj]

BIOLOGY

i dont know how to read ventricle graphs (mcq 14 june 2006) and i have seen that there are 4-5 questions concerning these types of graphs in past papers so can anyone pleeeeeeeease explain how to read these graphs ???

anyone pleaseee ?

 

[ashiqbal]

anyone pleaseee ?

remember this point> the valves will open only if the pressure behind them is greater than the pressure forward. for example if u look at point A, the pressure in ventricle becomes greater than pressure in atrium, so to prevent backflow, atrioventricular valves(in this case bicuspid valve) close. At point B, the pressure in ventricle becomes greater than pressure in aorta, so the semilunar valves open. At point C, the pressure in ventricle decreases to less than pressure in aorta, so the semilunar vavles close to prevent backflow. At point D, the pressure in ventricle again falls to less than atrium, so the atrioventricular valves open, allowing blood to flow from atrium to ventricle

 

[multixamza01]

can any one explain 5090 s05 qp 1 mcq no 40 and 37 and 12??

12 - the plant will lose some of it's roots and some maybe shortened during digging! Less roots , means less water absorbed , means less water transported means a piyas se pagal plant . Thus it wilts

37 - There are two possibilities . One that the male is homozygous dominant , which means his children will have the blood groups A and B .
Second possibility is that he is heterozygous dominant , which means his children will have B and AB blood groups .

As we have to chose the possible blood groups , we chose D .

40 - let the alleles be : H - dominant allele ; h - recessive allele .

One person has Hh genotype , and the other has hh genotype ( info derived from question )

Make the cross , we get Hh , hh , Hh and Hh genotypes . Which means
Ratio of
Children with Huntington's : Children not with Hungtinton's
2 : 2
1 : 1

Therefore the probility is 1/2 => O.5 => Option C

 

[bogus]

Please can someone explain the uses of transistors as simply as possible without copy pasting it off the net. ... would really appreciate your help

 

[Rimsa]

Please can someone explain the uses of transistors as simply as possible without copy pasting it off the net. ... would really appreciate your help

errr lets wait for sum1 but heres' one thing... why do u bother?? its optional! leave it and prepare the rest of syllabus

 

[SalmanPakRocks]

Please can someone explain the uses of transistors as simply as possible without copy pasting it off the net. ... would really appreciate your help

transistors are the device which are connected in the potential divider networks. These are semi conductor devices and act as a gate which allow the current to pass through the circuit! They only work when there is a current of more than 0.6 A

 

[bogus]

errr lets wait for sum1 but heres' one thing... why do u bother?? its optional! leave it and prepare the rest of syllabus

its always better to have options than to restrict oneself and get stuck

 

[bogus]

transistors are the device which are connected in the potential divider networks. These are semi conductor devices and act as a gate which allow the current to pass through the circuit! They only work when there is a current of more than 0.6 A

I that all we need to know about them ... also can u explain why they work only when a voltage is applied across its base??

 

[fatikhalid]

12 - the plant will lose some of it's roots and some maybe shortened during digging! Less roots , means less water absorbed , means less water transported means a piyas se pagal plant . Thus it wilts

37 - There are two possibilities . One that the male is homozygous dominant , which means his children will have the blood groups A and B .
Second possibility is that he is heterozygous dominant , which means his children will have B and AB blood groups .

As we have to chose the possible blood groups , we chose D .

40 - let the alleles be : H - dominant allele ; h - recessive allele .

One person has Hh genotype , and the other has hh genotype ( info derived from question )

Make the cross , we get Hh , hh , Hh and Hh genotypes . Which means
Ratio of
Children with Huntington's : Children not with Hungtinton's
2 : 2
1 : 1

Therefore the probility is 1/2 => O.5 => Option C

thanx..