Biology; Chemistry; Physics: Post your doubts here!

[***amd***]

View attachment 36083 Assalamualaikum Wr Wb...
Can someone please tell me what total transfer is? How to calculate it? etc...

Wa Alayikum Assalam
the total amount of heat energy transferred from one object/medium to other object/medium (in Joules), sorry i dont remember how to calculate. I'll try to post it

 

[***amd***]

I'm appearing for biology privately and without any tutor, so can someone give me any tips on the theory? I can solve the ATP really good except magnification, so can someone help me with that?

for magnification, solve it through the mathematical concept of ratios
like if u are given a figure 1 of a cell, and a larger size figure 2 of the same cell, measure the corresponding lengths of both. you'll be provided with the magnification of either of the two figures.
for example...
fig.1 : fig.2
4 : 10 ------> corresponding lengths of the figures
1000: x -------> magnification of the figures

4/1000 = 10/x
x = 1o * 1000/4
x = 2500

 

[Eimaan Aamir]

Thank you!
Also, What do I do with English? I mean, practice or what?

 

[***amd***]

Thank you!
Also, What do I do with English? I mean, practice or what?

ur welcome
english language or english literature?

 

[Eimaan Aamir]

English as a second language. Thanks again man, you be the best!

 

[Lilly2318]

Physics


40 An isotope X is radioactive and has a half-life of 4 years. A sample initially contains 8000 atoms

of X.

After how many years will the sample contain 1000 atoms of X?

A 4 B 8 C 12 D 16

Ans-C


38 Tritium is a radioactive isotope of hydrogen with a half-life of 12 years.

If a sample starts with 40 million atoms of tritium, how many atoms of tritium will be left after 12

years?

A 40 million

B 20 million

C 10 million

D 5 million

Ans B


40 The background count rate in a laboratory is 10 counts / min.

The measured count rate from a radioactive source is 410 counts / min, which includes the

background.

The half-life of the source is 5 days.

What is the measured count rate after 15 days?

A 10 counts / min

B 50 counts / min

C 60 counts / min

D 110 counts / min

Ans-C

any help here some 1 plz brief

 

[***amd***]

English as a second language. Thanks again man, you be the best!

its all just reading and writing.

 

[asadalam]

Physics


40 An isotope X is radioactive and has a half-life of 4 years. A sample initially contains 8000 atoms

of X.

After how many years will the sample contain 1000 atoms of X?

A 4 B 8 C 12 D 16

Ans-C


38 Tritium is a radioactive isotope of hydrogen with a half-life of 12 years.

If a sample starts with 40 million atoms of tritium, how many atoms of tritium will be left after 12

years?

A 40 million

B 20 million

C 10 million

D 5 million

Ans B


40 The background count rate in a laboratory is 10 counts / min.

The measured count rate from a radioactive source is 410 counts / min, which includes the

background.

The half-life of the source is 5 days.

What is the measured count rate after 15 days?

A 10 counts / min

B 50 counts / min

C 60 counts / min

D 110 counts / min

Ans-C

any help here some 1 plz brief

Radioactive elements have half-lives and after each half-life,their atom number is halved,e.g 2000 to 1000 in 10 days if half life of 10 days,and then 5000 after further 10 days and so on.

1. Isotope X has HF of 4 years hence after 4 years,its number will be 4000,then after further 4000/2 =2000,then 2000/2= 1000.Hence after 3 HFs,that means 3x4=12 years.

Rest you can follow through this concept.

 

[Lilly2318]

Radioactive elements have half-lives and after each half-life,their atom number is halved,e.g 2000 to 1000 in 10 days if half life of 10 days,and then 5000 after further 10 days and so on.

1. Isotope X has HF of 4 years hence after 4 years,its number will be 4000,then after further 4000/2 =2000,then 2000/2= 1000.Hence after 3 HFs,that means 3x4=12 years.

Rest you can follow through this concept.

Thank u

 

[Ishtiaque]

anyone can help me with the idea of magnetic screening in O level physics???

 

[mohsina asif]

guys, with hardly any time left for cies i wanted to ask a really general question. i am doing the prep like chapter classified, chapter classified and so on. but everyone says that do 2002-2013 yearly, (teachers do) but i do not have time so can it be like i just do last 5 years past papers once i am done with classifieds pluss maths. MY SIR EXPECTS A DISTINCTION FROM ME AND ITS GETTING TO MY HEAD BECAUSE I AM NOT WORKING ALL THAT HARD FOR IT. I mean i have to study for add math too :S

 

[Dark Destination]

guys, with hardly any time left for cies i wanted to ask a really general question. i am doing the prep like chapter classified, chapter classified and so on. but everyone says that do 2002-2013 yearly, (teachers do) but i do not have time so can it be like i just do last 5 years past papers once i am done with classifieds pluss maths. MY SIR EXPECTS A DISTINCTION FROM ME AND ITS GETTING TO MY HEAD BECAUSE I AM NOT WORKING ALL THAT HARD FOR IT. I mean i have to study for add math too :S

What subject does he expect a distinction in?

And you started off your post saying you wanted to ask a question, but you never did. You just told what you're doing, and what your sir expects from you. Be more specific about your question, please?

 

[mohsina asif]

Should i write it again in capsloack?
BUT I DO NOT HAVE TIME SO IS IT OK TO JUST DO LAST FIVE YEARS OF PAST PAPERS? (Do they promise enough prep if you are done with classifieds)
And Maths. I said Maths.

 

[Dark Destination]

Should i write it again in capsloack?
BUT I DO NOT HAVE TIME SO IS IT OK TO JUST DO LAST FIVE YEARS OF PAST PAPERS? (Do they promise enough prep if you are done with classifieds)
And Maths. I said Maths.

You can get a distinction in maths, even after doing 3 years of past papers, and if you fully concentrate on the day of your 'maths-distinction-deciding exam' and make no mistakes.

I know people who solved the entire classified, did 20 years of past papers, but ended up losing the distinction, due to a silly mistake or two.
So it's not about how much you practice, but how 'well' you understand the concepts.

 

[***amd***]

guys, with hardly any time left for cies i wanted to ask a really general question. i am doing the prep like chapter classified, chapter classified and so on. but everyone says that do 2002-2013 yearly, (teachers do) but i do not have time so can it be like i just do last 5 years past papers once i am done with classifieds pluss maths. MY SIR EXPECTS A DISTINCTION FROM ME AND ITS GETTING TO MY HEAD BECAUSE I AM NOT WORKING ALL THAT HARD FOR IT. I mean i have to study for add math too :S

do as much as you can.
well distinction is actually 90% luck.

You can get a distinction in maths, even after doing 3 years of past papers, and if you fully concentrate on the day of your 'maths-distinction-deciding exam' and make no mistakes.

I know people who solved the entire classified, did 20 years of past papers, but ended up losing the distinction, due to a silly mistake or two.
So it's not about how much you practice, but how 'well' you understand the concepts.

and i disagree dude. practice matters a lot!

 

[mohsina asif]

Practice does but so do concepts. Its just that time is the biggest issue here. I do not have enough time. Distinction is the biggest deal no? Its the competition between the best of the best. Too much to ask for tbh
So basically, should doing the sciences k last 5 years past papers be enough? (for A*)

 

[***amd***]

Practice does but so do concepts. Its just that time is the biggest issue here. I do not have enough time. Distinction is the biggest deal no? Its the competition between the best of the best. Too much to ask for tbh
So basically, should doing the sciences k last 5 years past papers be enough? (for A*)

ok, how many subjects are u taking this may june? and which ones?

 

[Dark Destination]

Practice does but so do concepts. Its just that time is the biggest issue here. I do not have enough time. Distinction is the biggest deal no? Its the competition between the best of the best. Too much to ask for tbh
So basically, should doing the sciences k last 5 years past papers be enough? (for A*)

Maths at O-Level is basic stuff. If you're good at maths, you must already know what i mean.
If your sir expects a distinction from you, you must be good at it.

Best of the best? Only a few people get full marks in maths, all over the world. All you have to do is get full marks. That's it.
And full marks can only be gotten if you have good concepts, and you don't make silly mistakes. That's all there is to it.
Even if you practice a million past papers, but make a 'silly' mistake, of rounding, or write cm instead of mm on the paper, you lose the distinction.
So, where did the 'practice' go now? It's about luck, and having good concepts and a good IQ.

To sum it up, good understanding of the syllabus content, with past paper practice (3 years, or 5 years, or whatever) and luck = Distinction.

 

[mohsina asif]

ok, how many subjects are u taking this may june? and which ones?

7, Eng, Math, Islamiat, Phy,Chemistry, Biology, Add math

 

[mohsina asif]

Maths at O-Level is basic stuff. If you're good at maths, you must already know what i mean.
If your sir expects a distinction from you, you must be good at it.

Best of the best? Only a few people get full marks in maths, all over the world. All you have to do is get full marks. That's it.
And full marks can only be gotten if you have good concepts, and you don't make silly mistakes. That's all there is to it.
Even if you practice a million past papers, but make a 'silly' mistake, of rounding, or write cm instead of mm on the paper, you lose the distinction.
So, where did the 'practice' go now? It's about luck, and having good concepts and a good IQ.

To sum it up, good understanding of the syllabus content, with past paper practice (3 years, or 5 years, or whatever) and luck = Distinction.

You make it all sound so easy. But i really wish its actually like this.. Thank you anyway.
What about physics, chemi, bio? Whats the general revision pattern for it. Like final and overall one.