Biology; Chemistry; Physics: Post your doubts here!

[irfan.kheerdali]

papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s11_qp_22.pdf. qu A6(b) please helpppppp please

 

[Honey Bee Bentley]

whats the diference between bistable and astable circuit?

 

[irfan.kheerdali]

hey guys i need some help. physics p22 oct/nov 12 qu.9 (b)(ii),(c),(d)(i),(ii) plzzzzz.exams next weekkkkkkk helppppppppppppp. (Those who help will get likes)

 

[AAAYY***]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w05_qp_2.pdf

question11 part b (ii) part 2

 

[Nabeel.Ahmad]

When a cyclist cycles uphill the energy conversion is from the chemical energy in his body to Gravitational Potential Energy due to upper position on the Hill top. But as s/he moves uphill , some chemical energy is also converted to kinetic energy. But it is not mentioned in the Mark Scheme. Could u plz explain?

Kinetic Energy is the energy related to Movement.
Gravitational Potential Energy is related to the position of the object, it's height from the ground.

As the Cyclist moves up the hill, the stored Chemical Energy in his body, is used to cycle and move uphill. As he moves up, we say the Chemical Energy is converted into Gravitational Potential Energy.
But, in O-Level we deal with the relation between Kinetic and G.P Energy, when we talk about moving upwards.
Whenever we talk about an object, moving up to a certain height. The gravitational potential energy will be maximum at the top height, and it will be zero, when the object is at the ground. Likewise, the Kinetic Energy will be zero at its maximum height, and maximum, just before the object hits the ground.
As an object moves upwards, we say its Kinetic Energy is being converted into Gravitational Potential Energy.
As the object descends to the ground, its Gravitational Potential Energy is being converted into Kinetic Energy, and the object Accelerates.

So, when the Cyclist is moving up the hill, his Kinetic Energy is being converted into Gravitational Potential Energy as he elevates from the ground. No Chemical Energy is converted to Kinetic. Hope you get my point.

 

[Nabeel.Ahmad]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w05_qp_2.pdf

question11 part b (ii) part 2

Q11. b(ii)

1. You have to find the Current I-w, by using the graph. See the corresponding value of Current for 12 Volts of Potential Difference, for the Wire W.
2. Same thing. Use the graph to Find I-l for the Lamp, corresponding value to 12 Volts.
3. Total Current, add the two answers in 1 and 2. Since, in parallel the sum of currents in two separate paths is equal to total current.
4. We have to find Resistance of Wire W. Use the formula, Resistance = Voltage/Current. We know the Voltage, that is 12 Volts. The Current I-w we found in 1.

 

[Fazal Warraich]

Can anybody help please? Resources n tips needed on the following subjects:
English
Maths
Physics
Chemistry
Computer Studies
Urdu

O-Levels student goin to appear in May/June 2K14

May Allah bless u n grant us success in this world n the hereafter ​

 

[Fazal Warraich]

P.S ur notes on Pak.St n Islamiat helped me alot thnx XPC got A* n A respectively looking forward for your guidance once again

 

[Enferno]

whats the diference between bistable and astable circuit?

A bistable circuit is a sort of electronic switch: it may use fancy logic, but ultimately it is just a switch that has two 'states', like on and off, or bright and dim. And there is a way that the circuit can be set to one 'state' or the other. So maybe when it is dark in the room, the switch is set make the television screen dimmer, and when it is light, the screen gets brighter. Or a night-light comes on when it is dark in the room. Some condition has to change to make anything happen. Maybe a person throws a switch. A light-switch is a simple bistable circuit.

An astable circuit is one that is going from one state to the other, back and forth, constantly. Lets say it is going on and off, and on and off. it does not need to be turned on and of. That is part of the circuit itself.

That does not mean that the length of the 'on' is the same as the length of the 'off', but it does mean that it never stops switching back and forth. A flashing light is like that. And the 'clock' that makes your computer do 3,000,000,000 logic steps a second (3 gigaherz) is that kind of circuit.

Short: Astable : No stable state...go on oscillating
Bi-stable: has two stable states....need trigger to go from one stable state to another.

 

[tdk]

Can anybody send me the May 2013 Cambridge O Level QP AND MS for Physics, Chemistry, Maths D, Add Maths and Biology? IT'S URGENT!!!!!!!!!!!!!!!!

 

[tdk]

Can anybody help please? Resources n tips needed on the following subjects:​

English​

Maths​

Physics​

Chemistry​

Computer Studies​

Urdu​

​

O-Levels student goin to appear in May/June 2K14​

​

May Allah bless u n grant us success in this world n the hereafter ​

Plz ask specific questions here: [email protected]

 

[tdk]

Re: Biology,Chemistry & Physics Help Available Here !

sorry about mixing it up.... i was in a hurry.... and yes. i did get but i was a little stuck on a 87 past paper question.... so no biggie. =) thanx btw.

Could u plz give me the question papers before 2000 ? Thank u so much.

 

[tdk]

Re: Biology,Chemistry & Physics Help Available Here !

Wassalam!
Topic made sticky.

Can anybody send me the May 2013 Cambridge O Level QP AND MS for Physics, Chemistry, Maths D, Add Maths and Biology? IT'S URGENT!!!!!!!!!!!!!!!!

 

[Sahana :)]

Hey guys. Any one know where i can learn about anion reactivity series? I tried using Google but i couldn't find anything useful. Help me please?! Thanks a ton!

Sahana

 

[Sahana :)]

Studies are still taking place – there has been this ‘Faster-than-light neutrino anomaly’ discovery, recently – this particular neutrino travels faster than the speed of light – BUT analysis are still taking place – we can’t hands down say anything about it.

Also, is that even in our syllabus?

Wasnt this speed of the neutrino recorded wrong due to some loose wire connections? What i heard later was that, it has been proven that these neutrinos are fast- but still slower than the speed of light. Do correct me if i am mistaken!

 

[Sahana :)]

Studies are still taking place – there has been this ‘Faster-than-light neutrino anomaly’ discovery, recently – this particular neutrino travels faster than the speed of light – BUT analysis are still taking place – we can’t hands down say anything about it.

Also, is that even in our syllabus?

Wasnt this speed of the neutrino recorded wrong due to some loose wire connections? What i heard later was that, it has been proven that these neutrinos are fast- but still slower than the speed of light. Do correct me if i am mistaken!

 

[Sahana :)]

Studies are still taking place – there has been this ‘Faster-than-light neutrino anomaly’ discovery, recently – this particular neutrino travels faster than the speed of light – BUT analysis are still taking place – we can’t hands down say anything about it.

Also, is that even in our syllabus?

Wasnt this speed of the neutrino recorded wrong due to some loose wire connections? What i heard later was that, it has been proven that these neutrinos are fast- but still slower than the speed of light. Do correct me if i am mistaken!

 

[Nabeel.Ahmad]

Hey guys. Any one know where i can learn about anion reactivity series? I tried using Google but i couldn't find anything useful. Help me please?! Thanks a ton!

Sahana

SO4-2
CO3-2
NO3-1

F-
Cl-
Br-
I-

OH-

[Ease of Discharge on the Anode increases downwards, re-activity decreases downwards]

 

[tdk]

Hey guys. Any one know where i can learn about anion reactivity series? I tried using Google but i couldn't find anything useful. Help me please?! Thanks a ton!

Sahana

As far as I know there is no such reactivity series. You can only remember the anions in order of increasing ease of their discharge at the anode during electrolysis namely, Sulfate, Nitrate, Chloride, Bromide, Iodide, Hydroxide. If I can find any mnemonic or memory aid I'll let u know later.

 

[tdk]

Kinetic Energy is the energy related to Movement.
Gravitational Potential Energy is related to the position of the object, it's height from the ground.

As the Cyclist moves up the hill, the stored Chemical Energy in his body, is used to cycle and move uphill. As he moves up, we say the Chemical Energy is converted into Gravitational Potential Energy.
But, in O-Level we deal with the relation between Kinetic and G.P Energy, when we talk about moving upwards.
Whenever we talk about an object, moving up to a certain height. The gravitational potential energy will be maximum at the top height, and it will be zero, when the object is at the ground. Likewise, the Kinetic Energy will be zero at its maximum height, and maximum, just before the object hits the ground.
As an object moves upwards, we say its Kinetic Energy is being converted into Gravitational Potential Energy.
As the object descends to the ground, its Gravitational Potential Energy is being converted into Kinetic Energy, and the object Accelerates.

So, when the Cyclist is moving up the hill, his Kinetic Energy is being converted into Gravitational Potential Energy as he elevates from the ground. No Chemical Energy is converted to Kinetic. Hope you get my point.

Here is the Question copied from the QP: 5054_s11_qp_22 (May/June 2011 , 5054/22 Question No 2,)

Fig. 2.1 illustrates the journey of a cyclist from point A to point B. Points A and B are at the same
height.

The cyclist starts from rest at A and pedals up and over a hill. Near the bottom of the hill, she
starts to brake and comes to rest at B.
(a) Describe the energy changes that take place as she pedals up the hill at constant speed.

Here is the answer from the Mark Scheme:

2 (a) chemical (potential) energy at start B1

gravitational/potential energy increases B1

thermal energy/heat/internal energy produced B1

So should we say that there is no K.E involved; But Chemical Potential Energy is being converted into G.P.E and Thermal Energy.