O level Physics (easy paper ) just tell how was it don't discuss the question till tomorrow !!

[Hashim Hayat]

Paper 1 was rather difficult!
Paper 2 was easy!!

 

[Hashim Hayat]

What was the answer to the 12th MCQ!
The one abt pressure?
3/2P
2/3P
2P
??

 

[Rimi]

The paper wasn't THAT easy. There were some tricky questions. P1 was weird. I just hope the percentile doesn't go very high :/

 

[MustafaMotani]

I chose A

was it arrow in the air or you knew dat.... ??

 

[MustafaMotani]

What was the answer to the 12th MCQ!
The one abt pressure?
3/2P
2/3P
2P
??

Neither of these
It was 2P/3

 

[khalil]

It was A , or in other word in the direction it was moving ( or as some are saying centripetal force) .

 

[MustafaMotani]

It was A , or in other word in the direction it was moving ( or as some are saying centripetal force) .

Got It..

 

[MustafaMotani]

I hope this comes handy to all I got this recently do have a look on it. It could be helpful in attempting the physics atp paper

 

[khalil]

Neither of these
It was 2P/3

I still have my queries for that mcq . The reason is most of the people used the formula pv=pv to attempt the question . This formula is applied when the container is some how decreasing in volume *Like a syringe * . As the containers were fixed .. one side had 200 cm3 of air .. the other had vacuum and a capacity of 100cm3 . When the valve opens .. firstly simple diffusion takes place ... causing air molecules to move from container A to B . Due to lessening of air molecules , the pressure decreases ... as the kinectic theory applies , the fewer the molecules the less chance of them striking the walls and hence less pressure . As its simple diffusion taking place and there is a movement of 100cm3 ... in container A only 100 cm3 is left , which is half the original . hence p/2 .

Those who can follow what i just wrote , please do see and some how prove that air molecules dont go from A to B but from B to A , cause thats the only way the answer could have been 2/3p

 

[Rimi]

I still have my queries for that mcq . The reason is most of the people used the formula pv=pv to attempt the question . This formula is applied when the container is some how decreasing in volume *Like a syringe * . As the containers were fixed .. one side had 200 cm3 of air .. the other had vacuum and a capacity of 100cm3 . When the valve opens .. firstly simple diffusion takes place ... causing air molecules to move from container A to B . Due to lessening of air molecules , the pressure decreases ... as the kinectic theory applies , the fewer the molecules the less chance of them striking the walls and hence less pressure . As its simple diffusion taking place and there is a movement of 100cm3 ... in container A only 100 cm3 is left , which is half the original . hence p/2 .

Those who can follow what i just wrote , please do see and some how prove that air molecules dont go from A to B but from B to A , cause thats the only way the answer could have been 2/3p

Lol. exactly. xD I used the same logic! my answer was P/2 too

 

[MustafaMotani]

I still have my queries for that mcq . The reason is most of the people used the formula pv=pv to attempt the question . This formula is applied when the container is some how decreasing in volume *Like a syringe * . As the containers were fixed .. one side had 200 cm3 of air .. the other had vacuum and a capacity of 100cm3 . When the valve opens .. firstly simple diffusion takes place ... causing air molecules to move from container A to B . Due to lessening of air molecules , the pressure decreases ... as the kinectic theory applies , the fewer the molecules the less chance of them striking the walls and hence less pressure . As its simple diffusion taking place and there is a movement of 100cm3 ... in container A only 100 cm3 is left , which is half the original . hence p/2 .

Dude you got it all messed up... u got that rite that pressure would decrease though. Initially when pressure was P total volume occupied was 200cm3, so when tap was opened total volume occupied turned out to be 300cm3 (200 previously and 100 new) so by using v1p1=v2p2, we get 200P=300P2 , thus P2 turns out to be 2P/3

 

[MustafaMotani]

I m pretty sure my logic is correct...

 

[khalil]

Lol. exactly. xD I used the same logic! my answer was P/2 too

That is the logic . I Teacher warned me strictly yesturday , not to use this formula if the containers own volume isnt decreasing * in otehr words only gas volume is decreasing
* . And its a very logical thing that if there is a vacum on the right side , the gas will travel towards the vacum , and if some gas travels towards the vacum , there will be a decrease in pressure in the orginal container .

 

[Rimi]

Dude you got it all messed up... u got that rite that pressure would decrease though. Initially when pressure was P total volume occupied was 200cm3, so when tap was opened total volume occupied turned out to be 300cm3 (200 previously and 100 new) so by using v1p1=v2p2, we get 200P=300x , thus x turns out to be 2P/3

Why would there be a change in volume? The volumes of the containors were fixed :/ Only the pressure changed.

 

[khalil]

Dude you got it all messed up... u got that rite that pressure would decrease though. Initially when pressure was P total volume occupied was 200cm3, so when tap was opened total volume occupied turned out to be 300cm3 (200 previously and 100 new) so by using v1p1=v2p2, we get 200P=300x , thus x turns out to be 2P/3

dude you do know the meaning of vacum ? It means there is nothing there . none . no molecules . NOTHING!!!! gas will MOVE!!! from one side to the other . You can't just add 100 cm3 of nothing in it .

and im pretty sure my logic is correct . But lets see when the marking scheme gets out .

 

[MustafaMotani]

Volume occupied by gas has increased....
Be positive if one container has 200 cm3 and one has 100cm3 and you know that we have to distribute air molecules in equal raion in both containers then 200 cm3 would have more molecules than in 100 cm3.
I got ur point thar air diffuses into 100cm3 container, but it is to ensure that only 1/3 molecules diffused not half

 

[khalil]

.

Volume occupied by gas has increased....
Be positive if one container has 200 cm3 and one has 100cm3 and you know that we have to distribute air molecules in equal raion in both containers then 200 cm3 would have more molecules than in 100 cm3.
I got ur point thar air diffuses into 100cm3 container, but it is to ensure that only 1/3 molecules diffused not half

he pressure P was the pressure inside the left container . it asked what will the value of pressure P . as were checking out pressure P only so no your not using the average container pressure . It could be that i read the question wrong , but i remember it saying pressure P . ( in such a case my answer would have been wrong )

 

[MustafaMotani]

thats the point diffusion depends upon conecentration (molecules/cm3) if there are 1-3rd molecules in 200cm3 (lets say 300 molcules were there in total, and so 1-3rd move to 100 cm3 then concentration will be 1molecule/cm3, and in 200cm3 will be (200/200) 1 molecule/cm3, this is when diffusion stops becox concentration is equal and so pressure reduces by 1-3rd... I know I m mixing things, hope u understand

 

[khalil]

thats the point diffusion depends upon conecentration (molecules/cm3) if there are 1-3rd molecules in 100cm3 (lets say 300 molcules were there in total, and so 1-3rd move to 100 cm3 then concentration will be 1molecule/cm3, and in 200cm3 will be (200/200) 1 molecule/cm3, this is when diffusion stops becox concentration is equal and so pressure reduces by 1-3rd... I know I m mixing things, hope u understand

Ohk if were taking the view of diffusion here let be clearify . The total available volume of gas is 200cm3 . and on the right side is 100 cm3 of vacum . At best you'd get 100cm3 on right and 100cm3 on the left . YOU CAN NOT GET 300cm3 of gas when there is only 200 cm3 of gas available .

 

[MustafaMotani]

.

he pressure P was the pressure inside the left container . it asked what will the value of pressure P . as were checking out pressure P only so no your not using the average container pressure . It could be that i read the question wrong , but i remember it saying pressure P . ( in such a case my answer would have been wrong )

what i really want to say is that pressure is distributed in the ratio of 2:1, Presseure in left turned into 2-3rd of P and container in rite had 1-3rd of P