Physics: Post your doubts here!

[Thought blocker]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w10_qp_12.pdf
Q5, 11, 22, 26 and 34. Please don't ignore this post at least XP

5)
x is 0.44. Add uncertainties. U get 0.03. (0.03/0.44)*100 = 7%

11)
The tension in the rope needs to balance out the weight of the student acting downwards, so since the total tension needs to be opposite and equal to the weight, Let tension in rope on left side be T1 and the tension on rope on right side T2 and :. Total tension = T1sino + T2sino
add them up... W= 2Tsino, rearrange to get T= W/ 2sino. Answer: B

22)
because since k is low for the first spring, the box will prevent it from breaking by over extending. Hence A

26)
We know that distance between two minima is given by λ/2 (example, distance b/w T and S is λ/2)
We also know that Microwave travels with the speed of light c i.e is 3 * 10^8 m/s
Given distance b/w each minima is 15 mm so total distance from T to P would be 15 * 4 = 60 mm

Now distance b/w:
T and S = λ/2,
S and R = λ/2
R and Q = λ/2
Q and P = λ/2
and them you get 2λ
so 2λ = 60*10^-3
hence λ = 0.03 m

We know that c = f * λ
So f = c / λ
f = ( 3 * 10^8 ) / ( 0.03 )
f=10GHz

34)
voltage decreases linearly so its supposed to be B : as rho increases, there would be more steepness in graph

 

[princessnoor]

28)
Weight acts downwards so since it's in equilibrium the electric force has to act upwards. Since the plate up is positive and attracting the drop, that drop has to have a negative charge.

hey can u help me with question 34 in this paper http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s11_qp_11.pdf

 

[Thought blocker]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_12.pdf

q 17! please helppp its simple i know but i m not gettin it!
also q 18 22 25

thanx

17)
At the bottom height is zero so mgh = zero
now going upwards..
2 block has height = 1 so mg1h
3 block = mg2h
4 block = mg3h
Sum up P.E ans is 6mgh

18)
efficiency = output power/input power
in this case its a generator so output power is P=VI = 230 x 32=7360
input power = E(potential) / time = Mgh/t = 200 x 8 x 9.81 = 15696
efficency = 7360/15696 x 100%=47% answer is D

22)
Basically, here they asked us to find volume of the crystal (cube), and then we are asked to find its length i.e is 3rd root of volume :¬
Find V from V = m / ρ and 3rd root (V) you'll get the answer

25)
IDK

 

[Ahmed Aqdam]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_12.pdf

q 17! please helppp its simple i know but i m not gettin it!
also q 18 22 25

thanx

25: Wire of the same material so same Young Modulus and same load is also given.
Extension is directly proportional to length and inversely to Area.
Half diameter so 1/4 Area and 1/4 length is given.
So extension will be same.

 

[Ahmed Aqdam]

hey can u help me with question 34 in this paper http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s11_qp_11.pdf

Resistance=p*l/A
As all sides are same of a cube so R=p/l
L is cube root volume so Resistance is p/cube root V

 

[xXGTZXx]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w12_qp_11.pdf

Q15

 

[Abdul Basit]

Q4 pls

 

[Ahmed Aqdam]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w12_qp_11.pdf

Q15

The weight is 0.15N and angle with the vertical is 30. Apply .15*tan30 to get the horizontal force.

 

[Ahmed Aqdam]

Q4 pls

1% of 2.00 is 0.02.
Total uncertainty is 0.04 as due to random error current is 2.00+-0.02

 

[Suchal Riaz]

If anyone has any problem ask me tag me 'suchal riaz' or text me if i am not available.

 

[..sacrifice4Revenge..]

What exactly is the rate of flow of electrons and whats the formula invovled

Which question. ._. ?

generally, what is it? :S

 

[Suchal Riaz]

generally, what is it? :S

what exactly is your question maybe I can help.
rate of flow of charged particle(such as electrons) is current
I=Q/t

 

[ShreeyaBeatz]

14: Moment is calculated by force*distance so they are inversely proportional. B is the correct graph for this.

17 and 35

37. When resistance is zero, p.d. will be zero and current passing thorugh the circuit will be maximum due to low resistance.
When resistance is maximum, p.d. will be maximum but current will not be zero as some current passes through.

39. Few particles will bounce back as most of the mass is concentrated at a point so a head-on collision only will result in this which has a low probability.

In 14, why is it B why not A??
And using the method you mentioned in Qno. 35 please solve - http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s06_qp_1.pdf question 33
it doesnt seem to work

Thank you

 

[Ahmed Aqdam]

In 14, why is it B why not A??
And using the method you mentioned in Qno. 35 please solve - http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s06_qp_1.pdf question 33
it doesnt seem to work

Thank you

Inversely proportional graphs are always like the one in B.
Suppose Fx is 24. So:
F is 1 when x is 24.
F is 2 when x is 12.
F is 3 when x is 8.
F is 4 when x is 6.
And so on.
Sketch these points and you will get this graph.

In this question the two parts are in series with one another so p.d. is divided between them. In the other one you mentioned, p.d. is same across the parallel combinations and is divided in the two resistors as they are in series with one another in both.

 

[..sacrifice4Revenge..]

Which formula is applied in this?!


Suchal Riaz Thought

 

[selena]

 

[selena]

 

[IGCSE13]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s13_qp_13.pdf Q19 , 30 , 35

 

[selena]

 

[sagar65265]

Which formula is applied in this?!


Suchal Riaz Thought

Electrons are negatively charged, and as such they will move from an area of lower potential to an area of higher potential. Also, they will move away from the negative terminal and towards the positive terminal (conventional current moves in the opposite direction, and in reality this flow of electrons is the current that actually transfers energy across the circuit).

Therefore, the current will go from the terminal on the right to the top-right corner of the circuit, move to the bottom right (point Y), move across the resistor to (point X) and then back to the positive terminal of the battery. Therefore, the current will be from Y to X (i.e. option C or D).

Furthermore, if the current is 4.8 Amperes, using the formula

Q = I * t

(Where Q is the charge that flows through a point in "t" seconds when a current of I Amperes is flowing)
we can say that

I = Q/t

So the current is equal to the rate of flow of charge past a point. Okay, so this has units Coulombs/Second, which is what we want (answer is also in same units).
So if the current is 4.8 Amperes, the rate of flow of charge is 4.8 Coulombs/Second.
How much is this? Let's see.

The charge on any 1 electron is 1.6 * 10⁻¹⁹ Coulombs. Therefore, to make up 1 Coulomb, we need 1/(1.6 * 10⁻¹⁹) = 6.25 * 10¹⁸ electrons.
But if 1 Coulomb is 6.25 * 10¹⁸ electrons per second, 4.8 Coulombs should be 4.8 * (6.25 * 10¹⁸) electrons per second, right?

Carrying out this calculation, we get 4.8 * (6.25 * 10¹⁸) = 30.0 * 10¹⁸ = 3.0 * 10¹⁹ electrons/second.

This flows in the direction of Y to X, therefore our answer must be A.

Hope this helped!
Good Luck for all your exams!