Physics: Post your doubts here!

[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!

 

[Thought blocker]

Which formula is applied in this?!


Suchal Riaz Thought

Which formula is applied in this?!


Suchal Riaz Thought

C ?

 

[Thought blocker]

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!

http://www.allaboutcircuits.com/vol_1/chpt_1/7.html
Electron flow is frm y to x so C

 

[Suchal Riaz]

Which formula is applied in this?!


Suchal Riaz Thought

there are a series of formulae to apply in this one. you must make sense first.
current = rate of flow of CHARGE
I = Q/t
charge of electron is e = 1.6E-19
(Q/t )/Q=1/t
if we divide I(total charge per time) by charge of one single electron we get number of electrons.
and the direction of current is from + to - but the direction of flow of current is from negative to positive.

 

[Suchal Riaz]

View attachment 44975

density = mass/volume
ρ=m/V
mass = ρV
----
both masses are same. the second liquid has twice density. so for mass to be same the volume must be half. total volume = 1.5 times initial volume.
final mass = twice the initial mass.
final ρ = 2m/1.5V = 4/3 ( m/V) = 4/3 ρ

 

[Suchal Riaz]

View attachment 44976

he is moving up at rate of 50cm/s means 0.5m/s
his mass is 80KG so his weight is almost 785N
power = work done per second= Force * distance/second = 785*0.5=392=0.39KW

 

[Suchal Riaz]

View attachment 44977 View attachment 44978

if he is at constant speed there is no resultant force so all forces cancel out so
air resistance = weight
kv=mg
v=mg/k
kinetic energy = 1/2 mv² = 1/2 m (mg/k)² = 1/2 m³g²/k² = m³g²/2k²