• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Physics: Post your doubts here!

Soldier313

Soldier313

Messages
958
Reaction score
3,499
Points
253
Hassi123 said:
PHY A2 HELP!
http://www.novapapers.com/images/PDF/CIE/A-LEVEL/Physics/2012nov/9702_w12_qp_41.pdf
Q9 bi } I get that we make a square wave but how do we figure out the cross over points?
Click to expand...


the graph will be a square wave with the initial coordinate being (0,5)
all the 3 graphs, (that is V1, V2 and Vout graphs) intersect at the same points (all of them above the x-axis)
whenever V2 > V1 , Vout will be +5v
whenever V1 > V2, Vout will be -5V
and at the points where the graphs intersect, there is a straight vertical line from +5 to -5 or vice versa
hope you understand......
Hassi123
 
A

azadii

Messages
22
Reaction score
5
Points
13
please someone post the physics As paper 2 of may june 2002 with mark scheme.i will very thankful for that. May Allah give all of us success
 
Soldier313

Soldier313

Messages
958
Reaction score
3,499
Points
253
azadii said:
please someone post the physics As paper 2 of may june 2002 with mark scheme.i will very thankful for that. May Allah give all of us success
Click to expand...

There you go.....
 

Attachments

  • 9702_s02_qp_2.pdf
    103.5 KB · Views: 2
  • 9702_s02_ms_2.pdf
    75.3 KB · Views: 5
Soldier313

Soldier313

Messages
958
Reaction score
3,499
Points
253
Oliveme said:
Can someone please explain this question? Question 7c) I don't understand at all why alternating current cause this to happen. Thank you. :)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_41.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_ms_41.pdf
Click to expand...


Aoa wr wb,

Look, when you have a sinusoidal alternating current, it implies that the direction of currents in both of the wires keeps changing directions, and since the currents are in phase, it implies that they have currents flowing in the same direction at any particular time.

Now, the method to obtain the direction of force on wire B, is to use Fleming's Left Hand Rule. But before doing this, the direction of magnetic field experienced by wire B must be obtained by using Right Hand Grip Rule on wire A.
Since the currents are constantly changing, the direction of magnetic field will keep on changing.
However, the force on wire B will always be towards the left (towards wire A) because the direction of magnetic field AND the direction of current are both changing, hence your thumb will subsequently point towards wire A.
The force varies from '0' to a maximum value and the variation is sinusoidal, this is obvious since a sinusoidal alternating current is being applied.
The last statement in the marking scheme which states 'at twice frequency of the current' is what i still quite don't get.

Hope it helped :)
 
Sijal Mirza

Sijal Mirza

Messages
48
Reaction score
34
Points
18
can u please tell me what topics from physics come in the ATP paper? (O-level) like in chemistry its mainly just Acids, Bases n Salts , Rate of reaction and Moles..
PLEASE HELP!
 
syed1995

syed1995

Messages
1,824
Reaction score
949
Points
123
salvatore said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s09_qp_2.pdf
No. 2 (b i).. it is a relatively simple question, but I'm kinda confused.
Change in momentum = momentum before - momentum after collision right?
So why did the marking scheme add the two velocities?

Please help me clear the doubt.. thanks!
Click to expand...


No. Change in momentum = final momentum - initial momentum = m(v-u)
taking <-- to be +

1.2(0.8) - 1.2(-4)
gives 5.76 Ns in the <-- direction as answer.

or if you take --> to be +

then

1.2(-0.8) - 1.2(4)
gives -5.76 Ns

the change is 5.76 Ns in <-- direction eitherway.
 
Oliveme

Oliveme

Messages
373
Reaction score
1,091
Points
153
Soldier313 said:
Aoa wr wb,

Look, when you have a sinusoidal alternating current, it implies that the direction of currents in both of the wires keeps changing directions, and since the currents are in phase, it implies that they have currents flowing in the same direction at any particular time.

Now, the method to obtain the direction of force on wire B, is to use Fleming's Left Hand Rule. But before doing this, the direction of magnetic field experienced by wire B must be obtained by using Right Hand Grip Rule on wire A.
Since the currents are constantly changing, the direction of magnetic field will keep on changing.
However, the force on wire B will always be towards the left (towards wire A) because the direction of magnetic field AND the direction of current are both changing, hence your thumb will subsequently point towards wire A.
The force varies from '0' to a maximum value and the variation is sinusoidal, this is obvious since a sinusoidal alternating current is being applied.
The last statement in the marking scheme which states 'at twice frequency of the current' is what i still quite don't get.

Hope it helped :)
Click to expand...
Thank you so much. It helped a lot. :)
JazakAllah Khairan.
 
salvatore

salvatore

Messages
382
Reaction score
315
Points
73
syed1995 said:
No. Change in momentum = final momentum - initial momentum = m(v-u)
taking <-- to be +

1.2(0.8) - 1.2(-4)
gives 5.76 Ns in the <-- direction as answer.

or if you take --> to be +

then

1.2(-0.8) - 1.2(4)
gives -5.76 Ns

the change is 5.76 Ns in <-- direction eitherway.
Click to expand...
I had got -5.76 Ns but thought that I'm wrong since the marking scheme gave 5.76 as the answer.
Thanks a lot :)
 
You must log in or register to reply here.
Top