Biology; Chemistry; Physics: Post your doubts here!

[TheStallion-Reborn]

i want help with this question. can anyone please explain this question to me?
Q no 4: part (b) nov 12 ppr
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_w12_qp_22.pdf
thanks in advance

can be many reasons actually mayb trying to kick sum1 on the tv he hates alryt jokes aside, the only thing related in our syllabus is adrenaline. talk about adrenaline in this

 

[Saad Mughal]

Yeah got it thanks Didn't know a simple acid carbonate reaction could be linked to the reactivity series like that

Chemistry is a funny subject. You never know what to expect.

 

[Saad Mughal]

What is the correct test for Hydrogen?
All examiner reports say "pops in a flame"
Does it mean we are not suppose to mention lighted splints? :/

Mark schemes give point to point answers, that does not mean that you can't provide explanations/proper sentences.
Whenever asked, just write,
Hydrogen gas makes a popping sound when a lighted splinter is brought near it.

 

[Saad Mughal]

ahh thankis! if u have a look at this marking scheme http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s08_ms_2.pdf and here is the paper;
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s08_qp_2.pdf
in question 6 i just saw the graph and the resistance was increasing, which straight away hit me that the current has to go down vecause R=V/I; and then when the resistance becomes constant, so does the current. But the mark scheme has this 'M1' written infront of the statement 'Decreases' I knew it was decreasing just by looking at the graph at did not apply any method here, so how will I be awarded the marks? AAANNDD...another thing, if you look at the mark scheme, though it considers the term 'becomes constant' correct, it also says accept '2 Amp' ..how is someone supposed to figure out the value of the constant current??

It's a 2 mark question which means you have to give two statements about the current, so:
As R=V/I, so as Resistance increases the value of the Current I decreases. As we proceed further, the resistance becomes constant and hence the current becomes constant.
You can also write, Current decreases as t increases, as we proceed further, current becomes constant.
^Any of these two statements would earn you full 2 marks, so yeah, you're answer will get the marks but remember to add full sentences! Don't just write "decreases or becomes constant"
As far as the ALSO in concerned, the also means that either answer is correct and will be accepted, you don't have to write both, just write one, the variety is there because some candidates write 0.2 A, others write constant. Hope you get it.

 

[Saad Mughal]

I NEVER get reversible equation...and then I stopped bothering because I didn't find any question on them. any important question regarding reversible reactions u have seen? and if u could please tell me what are the main points to be grasped in order to get hold of the topic :-/ and explain them a bit too like what is state of equilibrium n stuff and how will this knowledge be tested in the exam...

If you still have a problem with reversible reactions then read any of the two chapter notes below:
Notes credit: robinhoodmustafa.
If you have any further queries then just ask.

 

[fatima0000]

can be many reasons actually mayb trying to kick sum1 on the tv he hates alryt jokes aside, the only thing related in our syllabus is adrenaline. talk about adrenaline in this

but my question is that how can the chair be related to circulatory system

 

[TheStallion-Reborn]

but my question is that how can the chair be related to circulatory system

the chair is not involved any where it just talks about the rate at which the person's leg is kicking. when the person gets excited, adrenaline is released into the blood stream, which increses the rate at which heart beats. faster heartbeat=more rapid kicking. I hope this helps

 

[TheStallion-Reborn]

Mark schemes give point to point answers, that does not mean that you can't provide explanations/proper sentences.
Whenever asked, just write,
Hydrogen gas makes a popping sound when a lighted splinter is brought near it.

AND the splint is extinguished

 

[TheLeagueofShadows]

it is travelling downwards because it is emmited in that direction. however the part under consideration is it's direction as it leaves the magnetic field. I answered ur question earlier too. check it out it might help

Thanks!

 

[Saad Mughal]

AND the splint is extinguished

Well, I don't write the extinguishes part in 1 mark questions but yeah, it can be added too.

 

[fatima0000]

the chair is not involved any where it just talks about the rate at which the person's leg is kicking. when the person gets excited, adrenaline is released into the blood stream, which increses the rate at which heart beats. faster heartbeat=more rapid kicking. I hope this helps

i think u are answering me (a)(ii) but sorry to say that i dnt want explanation for this
my question was its part (b)which says
(b) Use your knowledge of how blood moves through the circulatory system to suggest an
explanation for why, after a few minutes, the chair falls forwards similar to the chair in
Fig. 4.2(b).
i hope u got it

 

[TheStallion-Reborn]

i think u are answering me (a)(ii) but sorry to say that i dnt want explanation for this
my question was its part (b)which says
(b) Use your knowledge of how blood moves through the circulatory system to suggest an
explanation for why, after a few minutes, the chair falls forwards similar to the chair in
Fig. 4.2(b).
i hope u got it

ohh!! im sorry my bad! u knw the whole of the path blood takes as it leaves the heart. right? the chair behaves as if weight is added to it's bottom, as demonstrated by the second picture. it is because the blood pressure in legs is far to low to force the blood up towards the heart against gravity. so the muscle contraction in legs help force the blood upwards. with the legs remaining stationary, there will be no muscle contractions to push the blood u and the blood will stay there in the legs as it arrives, adding to the weight at the bottom of the chair.

 

[fatima0000]

t

ohh!! im sorry my bad! u knw the whole of the path blood takes as it leaves the heart. right? the chair behaves as if weight is added to it's bottom, as demonstrated by the second picture. it is because the blood pressure in legs is far to low to force the blood up towards the heart against gravity. so the muscle contraction in legs help force the blood upwards. with the legs remaining stationary, there will be no muscle contractions to push the blood u and the blood will stay there in the legs as it arrives, adding to the weight at the bottom of the chair.

finally, thanks

 

[TheStallion-Reborn]

t
finally, thanks

haha ikr? sorry 4 da inconvenience

 

[zainabkhann]

What topics do i need to study for physics atp olevels? Can anyone please be specfic by telling me the topic names as i dont have the textbook with me, only have the past paper book, so the topic names will be helpful to me. Thanks

 

[TheStallion-Reborn]

HABER PROCESS;
In haber process what is the pressure supposed to be? is it 200 atp or 250 atp? my resources are clashing!

 

[Suchal Riaz]

thankyou but my question remains the same; what affect does an increased current have on a bulb and what affect does increased voltage have on a bulb (AS IN BRIGHTNESS ETC)

do u know Energy=power*time and power=Voltage*Current. so more current and voltage will result in more power which means more energy. more electrical energy means more light energy from bulb of more heat energy from heater and more kinetic energy from motor.
more voltage or current, more energy conversion. more electrical energy converted into light means brighter lamp.
this will help u more:

 

[TheStallion-Reborn]

View attachment 23752

do u know Energy=power*time and power=Voltage*Current. so more current and voltage will result in more power which means more energy. more electrical energy means more light energy from bulb of more heat energy from heater and more kinetic energy from motor.
more voltage or current, more energy conversion. more electrical energy converted into light means brighter lamp.
this will help u more:

thanku thanku................ thanku thanku thanku thanku ......thaannnnnkyouuuuuuu...

 

[ijlalm]

In a titration between an acid (in the burette) and an alkali, you may need to re-use the same
titration flask.
Which is the best procedure for rinsing the flask?
ARinse with distilled water and then with the alkali.
BRinse with tap water and then with distilled water.
CRinse with tap water and then with the acid.
DRinse with the alkali.
What is the correct option??

 

[TheStallion-Reborn]

In a titration between an acid (in the burette) and an alkali, you may need to re-use the same
titration flask.
Which is the best procedure for rinsing the flask?
ARinse with distilled water and then with the alkali.
BRinse with tap water and then with distilled water.
CRinse with tap water and then with the acid.
DRinse with the alkali.
What is the correct option??

id go wid B. cx any other option could cause misleading measurements. not sure though