Biology; Chemistry; Physics: Post your doubts here!

[Dark Destination]

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I think i understand what CIE means by ''stopping force''..
If a book is placed on a table, then the force acting on the table is ''Downwards'' and ''Equal to the weight of the stone''..
But if something is dropped from a higher platform, like in this case, the stone, then as it plunges towards the ground, it will gain Kinetic energy, and on impact the ground will have to provide a force equal to the weight to support its weight, but also an additional amount of force to cause its motion to stop. This case is different from a stone that is placed on the ground, and is not moving. In that case, the ground will just provide force equal to weight.

Since, the ground is providing force greater than weight, the force acting on the ground must also be greater than weight, according to Newtons third law of motion.

 

[Awesome12]

I think i understand what CIE means by ''stopping force''..
If a book is placed on a table, then the force acting on the table is ''Downwards'' and ''Equal to the weight of the stone''..
But if something is dropped from a higher platform, like in this case, the stone, then as it plunges towards the ground, it will gain Kinetic energy, and on impact the ground will have to provide a force equal to the weight to support its weight, but also an additional amount of force to cause its motion to stop. This case is different from a stone that is placed on the ground, and is not moving. In that case, the ground will just provide force equal to weight.

Since, the ground is providing force greater than weight, the force acting on the ground must also be greater than weight, according to Newtons third law of motion.

but that gain in Kinetic Energy will result in a loss of potential energy.
Also, won't the stone reach terminal velocity?

 

[Dark Destination]

but that gain in Kinetic Energy will result in a loss of potential energy.
Also, won't the stone reach terminal velocity?

Terminal Velocity is usually reached, when objects free-fall for a long time. A less distance, might not reduce the acceleration to such a great extent. But again, in this question the parameters about the distance the stone traveled are not given.
But even if Terminal Velocity is reached, the stone will still be in a state of ''motion''.. and additional force other than the one to support its weight, will be required by the ground to bring it IMMEDIATELY to rest.

 

[Awesome12]

Terminal Velocity is usually reached, when objects free-fall for a long time. A less distance, might not reduce the acceleration to such a great extent. But again, in this question the parameters about the distance the stone traveled are not given.
But even if Terminal Velocity is reached, the stone will still be in a state of ''motion''.. and additional force other than the one to support its weight, will be required by the ground to bring it IMMEDIATELY to rest.

Thanks
man we both sound like dexterous physicts

 

[Lilly2318]

Are transistors in syllabus? if so plz explain

 

[Dream.Eater]

Are transistors in syllabus? if so plz explain

It is there under section 25 of the 5054 syllabus but that entire section is optional. Any questions set on it is given as an alternative to another question

 

[Dream.Eater]

Could someone please help me out urgently because I have a physics test tomorrow.......
I need to know how to do part b2 and c

 

[asadalam]

Could someone please help me out urgently because I have a physics test tomorrow.......
I need to know how to do part b2 and c

That is one old,and really confusing question.

 

[Awesome12]

Could someone please help me out urgently because I have a physics test tomorrow.......
I need to know how to do part b2 and c

(b) 2 .
The glass wall of the cable is made up of 2 materials. The inner wall is made of a glass with lower refractive index, and the outer one is made out of a glass with a lower refractive index
The refractive index tells us how dense is a medium
Thus, the inner glass is denser than the outer glass
We already know that when light passes from a denser to a less denser medium, its speed increases, and it refracts AWAY FROM THE NORMAL
As a result, the angle of incidence is greater and it exceeds the critical angle, causing total internal reflection to occur.

 

[Dream.Eater]

(b) 2 .
The glass wall of the cable is made up of 2 materials. The inner wall is made of a glass with lower refractive index, and the outer one is made out of a glass with a lower refractive index
The refractive index tells us how dense is a medium
Thus, the inner glass is denser than the outer glass
We already know that when light passes from a denser to a less denser medium, its speed increases, and it refracts AWAY FROM THE NORMAL
As a result, the angle of incidence is greater and it exceeds the critical angle, causing total internal reflection to occur.

Thanks a lot. But I think what you meant was 'The inner wall is made up of glass of a higher refractive index,and the outer one is made of glass with a lower refractive index' You said lower for both walls. Could u please tell me what the part c calculation answers are as well.
Anyway thanks a ton youve helped me a lot

 

[Awesome12]

Thanks a lot. But I think what you meant was 'The inner wall is made up of glass of a higher refractive index,and the outer one is made of glass with a lower refractive index' You said lower for both walls. Could u please tell me what the part c calculation answers are as well.
Anyway thanks a ton youve helped me a lot

oops sorry
I will do so in my spare time
No problem

 

[Dream.Eater]

oops sorry
I will do so in my spare time
No problem

Okay.Thanks a lot !
Sorry for the trouble

 

[ZohaKhan]

importance of carbon cycle? any one?

 

[asadalam]

importance of carbon cycle? any one?

It's very important : P

 

[ZohaKhan]

It's very important : P

lol... i needed an answer

 

[Dream.Eater]

importance of carbon

Basically, the carbon cycle ensures that the carbon keeps rotating in the env. Carbon
is released into the atmosphere by combustion and respiration. It is 'lost' from the atmosphere by fossilization and photosynthesis. The cycle ensures that carbon is always present in the atmosphere as co2 so that plants could photosynthesize and also we could release locked away carbon by combusting fossil fuels.
The cycle is a long,descriptive process. You ought to check a good textbook for diagrams and detailed notes.
But still, I hope this helps!

 

[ZohaKhan]

yes it did alot ~! thanks

 

[sid2333]

To all lovely people here, I am really concerned about your honest replies on my question which I want to ask.
I am going to appear in May/June 2014 for Chemistry 5070. Alhamdullilah, I am passionate about getting a distinction in O level Chemistry. It has been my favourite subject and will be in the future. I have a sound knowledge of all the reactions, processes and QUALITATIVE ANALYSIS. Apart from the syllabus requirement for Chemistry, I have also a fine knowledge of tests which, however, are not a part of the syllabus. So moving on to my question, I want to ask if it is alright for me to write down that material which are not a part of syllabus though, but are legitimate? And this can lead me to have a distinction? Or what else I need to do in this petite amount of time to get myself prepare for DISTINCTION>>? I will be very happy to have your views on my question. Thank you, mhamzasiddiqui!

 

[Awesome12]

To all lovely people here, I am really concerned about your honest replies on my question which I want to ask.
I am going to appear in May/June 2014 for Chemistry 5070. Alhamdullilah, I am passionate about getting a distinction in O level Chemistry. It has been my favourite subject and will be in the future. I have a sound knowledge of all the reactions, processes and QUALITATIVE ANALYSIS. Apart from the syllabus requirement for Chemistry, I have also a fine knowledge of tests which, however, are not a part of the syllabus. So moving on to my question, I want to ask if it is alright for me to write down that material which are not a part of syllabus though, but are legitimate? And this can lead me to have a distinction? Or what else I need to do in this petite amount of time to get myself prepare for DISTINCTION>>? I will be very happy to have your views on my question. Thank you, mhamzasiddiqui!

no do not write irrelevant material
Writing irrelevant material makes the job harder for the examiner, and he will be less willing to account you for a distinction
You must remember that along with you, there are many others aiming for a distinction, and that not only should your concepts be clear, but your understanding skills and tackling new questions skills must be extraordinary.
Try to improve the way you write, like refer to terms and improve your language. In this time, try to practice as many past papers as possible

 

[sid2333]

Well, I'm not thinking about writing irrelevant material. For example, if examiner asks about the TEST OF NITRATE IONS, many of the candidates will write this:
"ADD AQUEOUS SODIUM HYDROXIDE THEN ADD ALUMINUM FOIL; WARM CAREFULLY: AMMONIA PRODUCED "
Whereas, I would write this:
"ADD CONCENTRATED HYDROCHLORIC ACID, THEN ADD FRESHLY PREPARED IRON (II) SULPHATE> : BROWN RING FORMS."

It's just an example. I know that this test is not the part of syllabus, but is definitely correct. Just like this,, there are many things!! mhamzasiddiqui