Physics: Post your doubts here!

[Thought blocker]

Q-6 full, help me
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s12_qp_22.pdf

 

[meerul264]

I need a list of topical past year questions for A2

Anyone know where can I get it?

 

[meerul264]

6(a)
Take note that how stationary waves are formed is often asked in exams.
So it's important to know how to write (just knowing how it is formed but not knowing how to write the answer will not give you credit).

How to answer:
So here is what I usually write when this question appears (after nth times):
"When two waves of the same frequency travels in the direction opposite to each other overlaps, the resultant displacements of the wave is
the sum of the displacement of individual waves. Producing nodes and anti-nodes. (The speed of the stationary wave is the speed of one of the overlaping waves."

6(b)
Although this kind of question is not frequently asked (from the past papers I've done so far), it's important for you to memorize the experiments to demonstrates stationary waves
(including how to draw the diagram).

According to the syllabus I've read, this include:
1. Demonstration using mechanical waves (stretched strings)
2. Demonstration using microwaves
3. Demonstration using air column

How to answer:
*The objective is to find the wavelength of sound in air using stationary wave.



"The source of sound is the microwave transmitter producing incident wave.
The receiver is the detector connected to a c.r.o to detect nodes and anti-nodes of the stationary wave.
The hard surface is made to reflect the incident microwave.

The incident microwave from the transmitter are made to be reflected off the hard surface. When the incident wave and reflected wave overlaps, nodes and anti-nodes are produced.
When the receiver is moved from the hard surface to the microwave transmitter, the detector will show alternating high and low readings, indicating the locations of anti-nodes and nodes respectively.
The wavelength of the stationary wave is 2 x (distance between adjacent nodes or anti-nodes)."

*If anyone can improve my answer or have a better answer for this question please let me know *

6(c)(i)



At the nodes, amplitude is minimum ( zero).
Since amplitude is proportional to intensity, the intensity is also zero ( I = k A^2).
At anti-nodes, amplitude is maximum.
Since amplitude is proportional to intensity, intensity is also at maximum. (I = k A^2)

6(c)(ii)

Use the formula v = f l where l is wavelength.

v = 340 m/s
l = 2 x (distance between adjacent nodes or anti-nodes)

 

[Faaiz Haque]

7 b iii, c
http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s05_qp_2.pdf

Please, I dont get it

 

[Thought blocker]

7 b iii, c
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s05_qp_2.pdf

Please, I dont get it

7biii)
V=IR
E=V+Ir
E=IR+Ir
So, I=V/R
=1.5/2 1..99=2
I=0.75A
E=3,I=0.75,R=2,r= ?
3=(0.75)2+0.75r
(3-1.5)/0.75=2 ohm
c)
Larger pd at R so it obv means smaller pd at r
so, smaller power dissipation at larger value of V
as, P=VI and I is same for R and r..

 

[The Godfather]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w09_qp_12.pdf
question-20,21,34,37,39,40

 

[Young Stunner]

I o

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w09_qp_12.pdf
question-20,21,34,37,39,40

I only got Q34. As we can see that the pd of Voltage is directly propotianal to Resistance so we can deduce that (the ratio of the two resistance * voltage = the pd across the resistor whose ratio we calculated)
So
Ratio of R1/R2 * emf of the battery = Votage across R1

 

[ZaqZainab]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w09_qp_12.pdf
question-20,21,34,37,39,40

20) they are asking strain energy which is= work done= area under the graph=((0.002*100)/2)=0.1J (we take 0.002 because we have to convert mm to meters) but if you look carefully the area we found is of a triangle where as in the graph its not exactly a triangle its a bit more so 1.1J it can be 2 cause that's just a lot more
21)E = F x L / delta L x A rearrange to get the ratio delta L / L on one side (change in length / original length) youll get >> delta L / L = F / E A (A = pi r ^2 ) = 20 / 2 x 10^11 x pi x (2.5 x 10^-4)^2 = 5.1 x 10^-4 multiply this by a 100 to get the % 5.1 x 10^-4 x 100 = 5.1 x 10^-2 %
34

I only got Q34. As we can see that the pd of Voltage is directly propotianal to Resistance so we can deduce that (the ratio of the two resistance * voltage = the pd across the resistor whose ratio we calculated)
So
Ratio of R1/R2 * emf of the battery = Votage across R1

37 Nucleons can never change
39 is just C It can not be A cause there is suppose to be a deflection not B cause they weight the same not D cause alpha particles are postive and so is the gold necule they repel and not attract
40 You know energy is J there is potential energy (mgh) Kinetic energy(0.5mv square) what is Joules derived units? kg⋅m2⋅s−2 <--- by using mgh
as they have given N derive it too it is kg⋅m⋅s−2so you want left hand side equal to right hand ride
kg⋅m2⋅s−2 = A,B,C OR D you will find B is the answer

 

[Young Stunner]

20) they are asking strain energy which is= work done= area under the graph=((0.002*100)/2)=0.1J (we take 0.002 because we have to convert mm to meters) but if you look carefully the area we found is of a triangle where as in the graph its not exactly a triangle its a bit more so 1.1J it can be 2 cause that's just a lot more
21)E = F x L / delta L x A rearrange to get the ratio delta L / L on one side (change in length / original length) youll get >> delta L / L = F / E A (A = pi r ^2 ) = 20 / 2 x 10^11 x pi x (2.5 x 10^-4)^2 = 5.1 x 10^-4 multiply this by a 100 to get the % 5.1 x 10^-4 x 100 = 5.1 x 10^-2 %
34
37 Nucleons can never change
39 is just C It can not be A cause there is suppose to be a deflection not B cause they weight the same not D cause alpha particles are postive and so is the gold necule they repel and not attract
40 You know energy is J there is potential energy (mgh) Kinetic energy(0.5mv square) what is Joules derived units? kg⋅m2⋅s−2 <--- by using mgh
as they have given N derive it too it is kg⋅m⋅s−2so you want left hand side equal to right hand ride
kg⋅m2⋅s−2 = A,B,C OR D you will find B is the answer

In ques 37 it can be proton or electron so how do we know what is the answer?

 

[LeQuavina]

Guys I have a problem. In paper 5 sometimes we have to give the answers in the table to 4-5 s.f for example but the numbers in the graph are to 2-3 s.f so do we round the numbers in the graph and then draw it?

 

[meerul264]

In ques 37 it can be proton or electron so how do we know what is the answer?

Nuclei contains only proton and neutron. (proton + neutron = nucleon)
The electrons are the one orbiting the nuclei.

So in physics its better to define isotopes to be the atoms that have the same number of protons but different number of neutrons in their nuclei.

 

[Faaiz Haque]

7biii)
V=IR
E=V+Ir
E=IR+Ir
So, I=V/R
=1.5/2 1..99=2
I=0.75A
E=3,I=0.75,R=2,r= ?
3=(0.75)2+0.75r
(3-1.5)/0.75=2 ohm
c)
Larger pd at R so it obv means smaller pd at r
so, smaller power dissipation at larger value of V
as, P=VI and I is same for R and r..

Thanks a lot!

 

[The Godfather]

20) they are asking strain energy which is= work done= area under the graph=((0.002*100)/2)=0.1J (we take 0.002 because we have to convert mm to meters) but if you look carefully the area we found is of a triangle where as in the graph its not exactly a triangle its a bit more so 1.1J it can be 2 cause that's just a lot more
21)E = F x L / delta L x A rearrange to get the ratio delta L / L on one side (change in length / original length) youll get >> delta L / L = F / E A (A = pi r ^2 ) = 20 / 2 x 10^11 x pi x (2.5 x 10^-4)^2 = 5.1 x 10^-4 multiply this by a 100 to get the % 5.1 x 10^-4 x 100 = 5.1 x 10^-2 %
34
37 Nucleons can never change
39 is just C It can not be A cause there is suppose to be a deflection not B cause they weight the same not D cause alpha particles are postive and so is the gold necule they repel and not attract
40 You know energy is J there is potential energy (mgh) Kinetic energy(0.5mv square) what is Joules derived units? kg⋅m2⋅s−2 <--- by using mgh
as they have given N derive it too it is kg⋅m⋅s−2so you want left hand side equal to right hand ride
kg⋅m2⋅s−2 = A,B,C OR D you will find B is the answer

20) Answer is 0.11
21) Answer is correct Ty
37) Answer is proton
39) Answer is B
40) Answer is A
Btw ty

 

[The Godfather]

I o

I only got Q34. As we can see that the pd of Voltage is directly propotianal to Resistance so we can deduce that (the ratio of the two resistance * voltage = the pd across the resistor whose ratio we calculated)
So
Ratio of R1/R2 * emf of the battery = Votage across R1

ty

 

[The Godfather]

Nuclei contains only proton and neutron. (proton + neutron = nucleon)
The electrons are the one orbiting the nuclei.

So in physics its better to define isotopes to be the atoms that have the same number of protons but different number of neutrons in their nuclei.

Answer is proton

 

[ahmed abdulla]

Can some draw the shape of the graph ? ( with explaination ) ?
9 (b) ii

 

[Thought blocker]

6(a)
Take note that how stationary waves are formed is often asked in exams.
So it's important to know how to write (just knowing how it is formed but not knowing how to write the answer will not give you credit).

How to answer:
So here is what I usually write when this question appears (after nth times):
"When two waves of the same frequency travels in the direction opposite to each other overlaps, the resultant displacements of the wave is
the sum of the displacement of individual waves. Producing nodes and anti-nodes. (The speed of the stationary wave is the speed of one of the overlaping waves."

6(b)
Although this kind of question is not frequently asked (from the past papers I've done so far), it's important for you to memorize the experiments to demonstrates stationary waves
(including how to draw the diagram).

According to the syllabus I've read, this include:
1. Demonstration using mechanical waves (stretched strings)
2. Demonstration using microwaves
3. Demonstration using air column

How to answer:
*The objective is to find the wavelength of sound in air using stationary wave.

View attachment 37811

"The source of sound is the microwave transmitter producing incident wave.
The receiver is the detector connected to a c.r.o to detect nodes and anti-nodes of the stationary wave.
The hard surface is made to reflect the incident microwave.

The incident microwave from the transmitter are made to be reflected off the hard surface. When the incident wave and reflected wave overlaps, nodes and anti-nodes are produced.
When the receiver is moved from the hard surface to the microwave transmitter, the detector will show alternating high and low readings, indicating the locations of anti-nodes and nodes respectively.
The wavelength of the stationary wave is 2 x (distance between adjacent nodes or anti-nodes)."

*If anyone can improve my answer or have a better answer for this question please let me know *

6(c)(i)

View attachment 37812

At the nodes, amplitude is minimum ( zero).
Since amplitude is proportional to intensity, the intensity is also zero ( I = k A^2).
At anti-nodes, amplitude is maximum.
Since amplitude is proportional to intensity, intensity is also at maximum. (I = k A^2)

6(c)(ii)

Use the formula v = f l where l is wavelength.

v = 340 m/s
l = 2 x (distance between adjacent nodes or anti-nodes)

Ty

 

[The Godfather]

Uncertainty

♣♠ Magnanimous ♣♠ Problem solved by him ?

 

[Faaiz Haque]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s07_qp_1.pdf

MCQ Q4,7,13,19,26,33,36

Sorry for so many, if anyone can help with even one of these questions that would be of great help to me.

 

[meerul264]

Answer is proton

Sorry if my explanation was not clear, but yes the answer is proton.

But the question was that whether the particle that have the same value in the nucleus of isotope is either electron or proton.
So that correct answer would be proton because proton is located within the nucleus,
but electron is orbiting outside the nucleus.