AS Physics (9702) Paper 22 Answers and Discussion

[Chucky]

This thread is only for those who wish to check answers, and I may not have all the answers correct, but I'll try and edit this post and make sure all the correct answers have been uploaded for you all to check!


Question 1: Power base units : kgm^2 s^-3
C has no unit (easy to prove)
speed of wind: 9.44 m/s

Question 2: Accel-time graph
a= 3.5
so the graph is a flat line at a=3.5 upto t=2 seconds. then it becomes zero after 2s

Momentum time graph:
momentum is 16.8 Ns at t=2s
line has a constant gradient upto t=2s and then becomes flat.

Question 3: Moments
Tsin50= 22.8 N
Weight of O is approx 19N
Mass is 19/9.81
A force has to be exerted by A to ensure there is no net force of the rod

Question 4: Brownian Motion
Apparatus: Light source, closed GLASS box with smoke particles in side and a microscope to view the particles from top
What we notice: Smoke particles moving in random zig-zag manner.
Properties of gas we can conclude: Have high energy in the particles and move in a random manner OR gasses fill up the volume of the container.

Question 5: Stationary Waves
Wavelength= 0.8m
How stationary waves are formed:
Progressive waves generated travel to the other end and REFLECT back. The reflected waves then SUPERIMPOSE with the original progressive waves and create regions of max disp (anti-nodes) and min disp (nodes).
Nodes correctly labelled.
length of PQ is 1.2m
Stationary wave at t+5ms is a straight line drawn from P to Q

use frequency to find the time period T of the wave which is 0.02s
t+5ms= 0.025s which is 1/4 of the wave period.
therefore the wave is a flat line.

Question 6: Electricity
Power= 3200W
Current = 13.3 A
Charge= Current X Time
Electrons flowing per second: 8.34 X 10^19

Question 7: Radioactivity
Alpha particle is a helium nuclei so the WXYZ part was easy
Mass doesn't seem to be conserved because MASS ENERGY is conserved. The change in mass is converted to other forms of energy such as K.E in the particles or photons OR gamma radiation.
Radioactivity is spontaneous meaning it is not affected by external factors such as pressure.

That's about it. If you have confusions DO NOT PM me. Ask here and others MAY help you out.

 

[FRENZYAMU]

Hoooooooraaayyyy ! my wave ws right,,,,,but messed up the momentum , cud've gotten near 56 minimum if i hadnt though

 

[Your-Blood]

For question 1 units of power are kg m^2 s^-3


You missed to raise a 2 over here.
But you must have done it right in exam.


Good job of compiling these answers these all are perfectly correct.

 

[Beaconite007]

Wow, a friend in real life gave me a screen shot of the same exact thing, but I had no idea it was from here O_O

 

[rose1700]

For question 1 :
last part : we were suppose to write speed 9.44 or 9.4
I think I wrote 9.4 :/

For question 3:
For mass I did 19/9.81
But wrote the final answer 1.9N should it be 1.93N
I thought we were supposed to write in 2 sig figure :/ but I wrote 19/9.81 instead of 19/10

Last part :
I wrote
" For a body to be in equilibrium resultant sun of all forces should be zero so a force must act on A to make the resultant sun of all the forces zero. "

Is this correct because I didn't wrote
A force has to be exerted by A to ensure there is no net force of the rod
For question 3
I didn't showed a light SOURCE but I showed light rays coming from one side and labeled it with light.
And I did didn't mentioned that the smoke cell was closed by glass lid would that be fine?

For question 5:
Also tell that how a stationary wave was produced by the apparatus?

 

[creative22]

Do you think drawing this would get me 2 marks at least ?
only first part of graph is correct

 

[Chucky]

Do you think drawing this would get me 2 marks at least ?
only first part of graph is correct

Not sure.

For question 3:
For mass I did 19/9.81
But wrote the final answer 1.9N should it be 1.93N
I thought we were supposed to write in 2 sig figure :/ but I wrote 19/9.81 instead of 19/10

You need to write 1.94

Last part :
I wrote
" For a body to be in equilibrium resultant sun of all forces should be zero so a force must act on A to make the resultant sun of all the forces zero. "

Is this correct because I didn't wrote
A force has to be exerted by A to ensure there is no net force of the rod

I think they'll accept that.

For question 3
I didn't showed a light SOURCE but I showed light rays coming from one side and labeled it with light.
And I did didn't mentioned that the smoke cell was closed by glass lid would that be fine?

Depends on how leniently they mark.

For question 5:
Also tell that how a stationary wave was produced by the apparatus?

I forgot to add that in, my bad.
Progressive waves generated travel to the other end and REFLECT back. The reflected waves then SUPERIMPOSE with the original progressive waves and create regions of max disp (anti-nodes) and min disp (nodes).

 

[Beaconite007]

Did we have to label a node at point P?
Also, in the moment's question, they gave us T which was 30 N.
30sin50 = 22.98 N
round it off to 2 sf and we get 23 N.

 

[Jinkglex]

I think the momentum one might be slightly wrong since it was moving with a force of 8.4N i believe, thus its Momentum would be 8.4 first second, 16.8 next, then constant at 16.8.

 

[Jobiii]

For the first part, to find the velocity, did you have to use that 55% efficency at all? Because in the question it said the output power "P" is "...", and in the equation it's also written P, so don't you just substitute it and find v?
also does Ms mean x10^6 seconds? because thats really long, like 700 hours
I got those three things wrong so mabey 47-48 marks I guess
do you think threshold will be 40+?

 

[Beaconite007]

For the first part, to find the velocity, did you have to use that 55% efficency at all? Because in the question it said the output power "P" is "...", and in the equation it's also written P, so don't you just substitute it and find v?
also does Ms mean x10^6 seconds? because thats really long, like 700 hours
I got those three things wrong so mabey 47-48 marks I guess
do you think threshold will be 40+?

Highly doubt it'd be above 40.
It was like an average physics paper, seemed easy but actually required critical thinking.
It'll hit 39, imo.
And yes, I got the wind speed wrong too. They said it was "P" in the question so I thought they gave the efficiency just to confuse us. I should've known better, they never give useless info.

 

[Jobiii]

Highly doubt it'd be above 40.
It was like an average physics paper, seemed easy but actually required critical thinking.
It'll hit 39, imo.
And yes, I got the wind speed wrong too. They said it was "P" in the question so I thought they gave the efficiency just to confuse us. I should've known better, they never give useless info.

Did you get like 7.7 r something? I'm thinking that is the right answer because it says it right there, output power "p"
For the second part of that question, why all of the wind energy isn't converted, I said "because the efficency is 55%", and I think that's why they put that there. You can't have "p" in the equation and then assign p a value, then have to convert it, that wouldn't make any sense

 

[talha196]

what two points did you guys write in the first question for why not all wind energy is transformed into electrical energy...?

 

[Saif Thara]

In the paper, there was a question to draw a graph of Acceleration and Momentum. For that we needed to take take force values from the graph given. Value of the force was 8.4 N, but I took 8N, I did all calculations using it. The shape of my graph is correct. So will I get marks for it and or my whole answer will be given zero ?

 

[Beaconite007]

Did you get like 7.7 r something? I'm thinking that is the right answer because it says it right there, output power "p"
For the second part of that question, why all of the wind energy isn't converted, I said "because the efficency is 55%", and I think that's why they put that there. You can't have "p" in the equation and then assign p a value, then have to convert it, that wouldn't make any sense

Yeah, it was denial at first for me too
I read the question carefully, and began calculating a new P, but then crossed it out and used the Power output they'd given.
Wonder if I'll get any marks for that :s

 

[shah zaib]

wasn't the stationary wave suppose to lag behind the wave drawn already by the phase angle of 90 degrees ?

 

[Jinkglex]

I dont see why the new way should be a flat line. Shouldnt it simply be a transverse wave having a 1/4th phase difference [90* i think] with the original wave? Flat line makes no sense to me :/

 

[HorsePower]

can anyone please explain the reason for a straghit line in the wave question?

 

[mahin_a96]

Any tips on solving paper 1 questions? That thing really screws me up :/

 

[Malik777]

What would be the threshold? :S