Biology; Chemistry; Physics: Post your doubts here!

[Awesome12]

Because velocity is in negative too.
x - (-y) = 47

Why is it negative?

 

[Dark Destination]

Why is it negative?

Change in direction.

 

[Awesome12]

Change in direction.

Thanks

 

[Awesome12]

Does this really work? Can someone explain this to me? How is this possible?

Ask suchal riaz. I think he knows it.

 

[Dark Destination]

Thanks

No problem.

 

[Dark Destination]

Suchal Riaz

 

[Suchal Riaz]

i uploaded this on my profile and now it has made into o level forum lol
actually there is nothing to break the law of physics. the forks are bent to their centre of gravity is at that exact point where the coin touches glass.
it's fairly easy to do at home.

 

[Awesome12]

No problem.

Another question. Same paper, question 3 (a) (ii). Why do we divide the moment M by 12?

 

[Dark Destination]

Another question. Same paper, question 3 (a) (ii). Why do we divide the moment M by 12?

I didn't read the question, but consider the direction of the force. And look at the distance perpendicular to it..
The force is acting leftwards, so pivot is down.

MOMENT = FORCE into PERPENDICULAR DISTANCE from LINE OF ACTION OF FORCE TO PIVOT.

 

[spacemaster960]

physics
• do calculations involving
part of a circuit,
whole circuit.
• explain what is meant by
fuse ratings,
circuit breaker settings.
• describe the effect of temperature increase on the resistance of
a resistor,
a filament lamp.
• describe the use of a voltmeter with different ranges.
• describe the use of an ammeter with different ranges

can anybody help me with these???

 

[Dark Destination]

Another question. Same paper, question 3 (a) (ii). Why do we divide the moment M by 12?

They're not always going to give you a see-saw with people sitting on each side.
Visualize Physics. Look at different situations, and it's not always going to be a see-saw.
Sometimes the forces won't even be parallel like in this case. The forces are perpendicular. The clockwise moment and Anti-clockwise moment have forces that are not parallel. One is acting leftwards creating an anticlockwise moment about P. One is acting downwards creating a clockwise moment. So for each consider the perpendicular distance.

 

[Mahnoorfatima]

The role of micro organisms on the root nodules in the nitrogen cycle? Anyone? Plus can anyone explain explicitly the mechanism of opening and closing up of the stoma during day and night?

 

[funky brat]

The role of micro organisms on the root nodules in the nitrogen cycle? Anyone? Plus can anyone explain explicitly the mechanism of opening and closing up of the stoma during day and night?

They are called the nitrogen fixation bacteria. They convert nitrogen in air to nitrates.
And the stoma thing, it's lengthy. :/
You need to mention the glucose concentration that decreases the water potenetial of the cell and the Pottasium ion theory.

 

[Mahnoorfatima]

They are called the nitrogen fixation bacteria. They convert nitrogen in air to nitrates.
And the stoma thing, it's lengthy. :/
You need to mention the glucose concentration that decreases the water potenetial of the cell and the Pottasium ion theory.

Yep I know about the glucose and the potassium ion theory but there's this question in M/J 2013 in which it says that what is the advantage of the difference in the guard cells at 13 00 and 1 00.
Plus why do crops that are grown genetically produce fewer offspring and less variations? M/J 2013

 

[funky brat]

Yep I know about the glucose and the potassium ion theory but there's this question in M/J 2013 in which it says that what is the advantage of the difference in the guard cells at 13 00 and 1 00.
Plus why do crops that are grown genetically produce fewer offspring and less variations? M/J 2013

Paper link and question number. There's must be some other information. At 1300 it would allow carbon dioxide to diffuse in beacuse at that time light is available and photosynthesis would occur.

 

[Mahnoorfatima]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_s13_qp_22.pdf
Question 1 part c.
Section B question number 6 b.

 

[funky brat]

At 13 hours the guard cells willl be open. Allow diffusion of CO2 inside > Photosynthesis > Diffusion of oxygen outside. Also allow evaporation of water hence regulating temperature.
At 11 hours they will be closed preventing excessive water loss by leaves.

 

[exploded diper]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_s13_qp_22.pdf
Question 1 part c.
Section B question number 6 b.

becuz the plants would not be exposed to too much air in a closed building.......their r less chances of insect living bout in building...so as there is lesser chance of insect and wind pollination........they can onlu polinate with the palnts in building rather thn those outside so less cross pollination wll occur. as also the plants are isolated from other plants tht r outside....so less variety and less viable seeds r produced.....

 

[Mahnoorfatima]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_s13_qp_12.pdf
Question 3?
And in question 4 why does the iodine test give black colour when we have BOILED amylase which means that the enzyme got denatured. Thus the enzyme wont act on it and the colour should be yellow.No?

 

[Nisa Mirza]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_s13_qp_12.pdf
Question 3?
And in question 4 why does the iodine test give black colour when we have BOILED amylase which means that the enzyme got denatured. Thus the enzyme wont act on it and the colour should be yellow.No?

One observes a black colour when starch is present in the solution. Boiled amylase is denatured and won't be able to break down the starch, so u got starch still intact in the solution.