Physics: Post your doubts here!

[Hassan Mirza Aziz]

Can anyone predict or have any idea whats coming in physics p33?

 

[Komail Sabba']

The elementary charge (1.6 x 10^-19) is a multiple of the differences of the given charges.

Is there a specific order to subtract from them?
Like: arrange from largest to smallest and subtract in order
Or: subtract in the given form
Or how?

 

[The Sarcastic Retard]

Use speed of approach and seperation concept.

Ok guys I have a question about momentum.
Assume a scenario where two masses of equal masses and acceleration are moving towards each other about to collide.
Can we predict their behavior after collision. Do they bounce back with same velocity or acceleration? Or stick together and stay stationary? Or is it impossible to predict?

 

[mehria]

extend it

but in s2014 v 51 ths isnt the case... the lower n upper ends are till the plotted points... they r nt extended... :/

 

[mehria]

...
I don't know. If it's from the markscheme, it says the lower end should PASS between ...... In my opinion, if this end at that point, the MS should have said 'the lower end should BE at point ....' + we don't know if the line is exactly at a point, there could be an error at that point?

actually, i haven't yet read much about how the practical papers should be tackled, so I can't help here (can't be 100% sure what to do here).
What did your teacher say about these?

he said nthng abt p 5.. (-_-)

 

[mehria]

...
I don't know. If it's from the markscheme, it says the lower end should PASS between ...... In my opinion, if this end at that point, the MS should have said 'the lower end should BE at point ....' + we don't know if the line is exactly at a point, there could be an error at that point?

actually, i haven't yet read much about how the practical papers should be tackled, so I can't help here (can't be 100% sure what to do here).
What did your teacher say about these?

http://maxpapers.com/wp-content/uploads/2012/11/9702_s13_qp_42.pdf
Q3 (a) (ii) y do we use cos for x?

 

[Debonny1]

How do we know if a sphere is a conductor if a graph of electric field strength against distance from the sphere is given?

 

[buckle_crackk]

A cannon fires a cannonball with initial speed v at angle α to the horizontal.


Which equation is correct for the maximum height H reached?
A H = v sinα / 2g
B H = g sinα / 2v
C H = (v sinα)2 / 2g
D H = g2 sinα / 2v

i found the vertical component = Vsina ...hence, options B and D are ruled out.... but why is the answer C?

 

[Ahmed Aqdam]

A cannon fires a cannonball with initial speed v at angle α to the horizontal.


Which equation is correct for the maximum height H reached?
A H = v sinα / 2g
B H = g sinα / 2v
C H = (v sinα)2 / 2g
D H = g2 sinA / 2v

i found the vertical component = Vsina ...hence, options B and D are ruled out.... but why is the answer C?

Apply 2as=v^2-u^2
a is -g, v is 0 and u is vsinα.
Insert these values to get C.

 

[..sacrifice4Revenge..]

I really need help with this concept:

http://prntscr.com/75vq5i

may june 11 42 q9 b.

how do we identify across which resistor is the input going to be?
for example, in this case. is the 4.5V going to go to the Non-iverting input from across the 1kV resistor or the strain gauge?

A generalised explanation is needed on this thing,not this question specific. since I struggle on every question of this kind.


Thanks a lot and God Bless!

 

[farhan980]

Just draw half rectangles with their heights at +5v and -5v since it can never exceed the supply. Each time, draw the half rectangle opposite to the vin , if the cycle of vin is +ve, draw vout at -ve and vice versa

Thank you very much but what about the width of the rectangle. Im still confused about that.

 

[TheJDOG]

Thank you very much but what about the width of the rectangle. Im still confused about that.

The width depends on where Vin is 0, so everytime the graph of Vin is 0 you switch the polarity try sketching it and upload it here so I check how you sketched it

 

[TheJDOG]

Could someone just give me a quick explanation with tips on how I should find the area under a graph when I'm asked to do so? Do I count the squares? Then what? Thank you

 

[mehria]

check at
http://physics-ref.blogspot.com/2014/07/9702-june-2013-paper-42-worked.html

bcoz at t=0, the displacement is not zero. if you plot a graph, the oscillations would correspond to a cos graph, not a sine.

for sine, when t=0, displacement is also zero


...well, this should also have been in your notes

yea but i was confused ...
thnks..

 

[..sacrifice4Revenge..]

http://physics-ref.blogspot.com/2014/08/9702-june-2011-paper-42-43-worked.html

thanks but I actually need the concept and not the answer.
why is the Potential taken across the 1kOhm resistor and not the strain gauge? how does that work every time, how do we decide across which resistor to take potential.

 

[mehria]

check at
http://physics-ref.blogspot.com/2014/07/9702-june-2013-paper-42-worked.html

bcoz at t=0, the displacement is not zero. if you plot a graph, the oscillations would correspond to a cos graph, not a sine.

for sine, when t=0, displacement is also zero


...well, this should also have been in your notes

http://maxpapers.com/wp-content/uploads/2012/11/9702_s12_qp_42.pdf
Q1 (c)(ii) i didnt get the ans in ms... wat do they mean by " ΔEP = Fx because F constant as x ! radius of orbit"

 

[farhan980]

The width depends on where Vin is 0, so everytime the graph of Vin is 0 you switch the polarity try sketching it and upload it here so I check how you sketched it

is this how i should do it ?

 

[mehria]

I really need help with this concept:

http://prntscr.com/75vq5i

may june 11 42 q9 b.

how do we identify across which resistor is the input going to be?
for example, in this case. is the 4.5V going to go to the Non-iverting input from across the 1kV resistor or the strain gauge?

A generalised explanation is needed on this thing,not this question specific. since I struggle on every question of this kind.


Thanks a lot and God Bless!

it is going across 1 kΩ resistor.. in such questions u'll always apply the concept of potential divider... the resistor n strain gauge acts as potential divider to the non-inverting input... that's y u cn see that the voltage across 1.0 kΩ is V1 ..ths is clearly indicated in the diagram...


just lyk the potential divider lyk above... instead of Vout lets suppose that it's V2
so the value of V2 is calculated as=> V2 = [(R2) / (R1 + R2) ] x Vin

the concept is very easy... just ignre the rest of the connections n focus on the wire that has strain gauge n resistor across it...

 

[mehria]

Could someone just give me a quick explanation with tips on how I should find the area under a graph when I'm asked to do so? Do I count the squares? Then what? Thank you

cn u post an example so that explaining it gets easier...

n in general u dnt need to count the squares... count the area of 1 cm square n then count the number of the squares having area of 1cm^2 .. then multiply the number of squares with the value of area of 1 square... u'll get ur ans...

 

[..sacrifice4Revenge..]

it is going across 1 kΩ resistor.. in such questions u'll always apply the concept of potential divider... the resistor n strain gauge acts as potential divider to the non-inverting input... that's y u cn see that the voltage across 1.0 kΩ is V1 ..ths is clearly indicated in the diagram...
View attachment 53800



just lyk the potential divider lyk above... instead of Vout lets suppose that it's V2
so the value of V2 is calculated as=> V2 = [(R2) / (R1 + R2) ] x Vin

the concept is very easy... just ignre the rest of the connections n focus on the wire that has strain gauge n resistor across it...

thank you soo much!

btw.. there's another thing, you got sometime?