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# The Physics PHYA2 thread! 5th June 2013 Watch

• View Poll Results: What mark do you think you got out of 70?
0-20
6
3.00%
21-40
12
6.00%
41-50
29
14.50%
51-60
79
39.50%
61-70
74
37.00%

1. (Original post by trentjoseph007)
JUST TO GET PEOPLES ATTENTION !!!

I think everyone misunderstood the last question on the paper. It was white light passing through a single slit. Look at the textbook page 202, figure 2. Apparently no one here realized it.
Uh oh...
2. The Unofficial Mark scheme People.. thanks to Lebron! can everyone please find what's missing and where the last question goes so we can properly estimate what we got. Thanks
(Original post by lebron_23)
PHYA1 (Provisional, and very shaky) Mark scheme;

Question 1 – Simple matter of working out forces and that stuff, efficiency question may cause problems though.

1) 6082N, which is 6100 to 2sf (2)
b) 9.5 degrees using arctan of 1000/6000 (2)
c) Acceleration was 9.2ms^-2 (2)
d) Can’t remember what this one was asking but I got 3.9x10^6 (not sure) (2)
e) I got 20.5% but I’m not sure as I’ve heard people give various answers (3)

Question 2 – Fairly straightforward question about projectiles.

2) Time taken was 0.55s (2)
b) The horizontal distance was 248m I think (2)
c) As both bullets have the same mass, S=ut will be smaller for the bullet with the lower horizontal velocity (3?)
-- Can’t remember if there was anything more to this question

Question 3 – Perhaps the best 6 marker they’ve ever given, very straightforward.

3) The ball begins to accelerate with a large acceleration as its weight force is (one of) the only forces acting as it begins to move. The gradient then begins to slowly decrease as the resistive forces begin to balance out the weight force. The ball finally reaches terminal velocity as the resistive forces balance out the weight force. Appropriate reference to Newton’s first law needed. Then the ball remains at that velocity, as there is no external force, give reference to Second Law. (6)
b) Initially a straight line indicating uniform acceleration, then a curve of decreasing gradient ending with the ball at terminal velocity. (3)

Question 4 – A decent question, I guess.

4) Weight of the ball was 0.44N (2sf) using volume of a sphere which is given in the data sheet!!! (4)
b)Hooke’s law states that force applied is proportional to the extension up to the limit of proportionality (2)
c) Gradient was roughly 1150/1100 Nm^-1needed (3)
d) Using the area of a triangle and then counting (roughly) 9 small boxes each of area 0.025 gave 1.08J (3?)
e) Straight line parallel to the first one but not finishing at zero as plastic deformation has occurred (2)
d) Plastic deformation means the object won’t return to its original shape/length once the load is removed (2)
f) Work is less as area under graph is less energy absorbed as heat and in permanent extension (1)

Question 5 – Wasn’t too bad..

5) Two conditions for TIR were an angle greater than the critical angle and moving from a medium of higher refractive index to lower (2)
b) Defining the frequency of a progressive wave. Just explain the equation? (1)
c) Speed of light in the object thing was 1.7x10^8 (2)
d) Proof that the angle was about 31.8 degrees using Snell’s Law
e) Critical angle was 51.1 degrees using 1/sinc (2)
f) Undergoes TIR as (20+31.9) > 51 (2)

Question 6 – Don’t even know, seemed cool..

6) First phase difference was 90 degrees or pi/2. Second was 270 degrees or 3pi/2 (2)
b) Oscillation between maximum and minimum amplitude; i.e moves up and down (2)
c) Polarisation only occurs in transverse waves; mention something about plane of polarisation (2)
d) Define frequency (1)
e) 750m (2)

Question 7 – I may have flopped

7) All of the light has the same wavelength (1)
b) Can’t really remember – According to Frogs491 its ‘Fringes larger so intensity equal’ -- If this is the graph of intensity, then (2)
c) I too cannot seem to remember this
e) Last part; white at central maxima and very bright as all of the wavelengths converge at the centre; blue tinge closer to central maxima and red tinge further away; not sure about anything else. (3)

That’s all I can remember guys. I’ve probably omitted quite a few things so if anyone can spot any mistakes, let me know and I’ll make amendments

EDIT: I'm going to start adding in the marks for each question slowly so that should be half done soon. If anyone can remember what the marks are for each question please let me know! Thanks.

Also, I can't remember where the question about the weight of the ball goes but it was 0.44N and worth (4) marks...

Guys, we're missing 4 marks so if anyone can remember anything...
3. Feel like poo. Rushed through and didn't see that they'd already given the speed of the light ray. For some reason I used the speed in a stupid vacuum :'(
4. My mark scheme

1a) square root of 1000 squared+ 6000 squared
1b) 32
1c) 9.2
1d) 3900000
1e) 22%

2a)0.55
2b) 240
2c) the horizontal displacement =ut. It takes the same time to falls and u is less and therefore the distance travelled is less

3a)
Inital quick acceleration shown by steep gradient
As it falls a drag force is produced
As the object falls the drag force on it increases reducing the resultant force
F=ma with respect to Newton's second law and so the acceleration decreases as it falls as shown by the gradient getting smaller
Eventually drag is equal and opposite to weight
Ball travels at constant Velocity shown by the straight part of the graph near the end of time
Reference to Newton's first law as it moves at a constant velocity as there is no resultant force
Some of the energy of the object is converted into internal energy of the oil
It finally hits the bottom as shown by the vertical line at the end

3b) I did a striaght line to about 3/4 the way up the line before it hit the fluid
Copied the graph from the page before for the second bit but starter it lower to show it's speed falls when it hits the oil
Striaght line at the end

4a) I got the wrong as I said f *proportional sign* KL and defined the terms
4b) 1200 n/m
4c) 9.4? I got this wrong I think I found how many squares there were and times by the area per square
4d) the object is permanently stretched and doesn't return to its inital length
4e) striaght line to the x axis but a bit to the right than the first list as there is extension at the end of unloading

5a) n1>n2
Angle of incidence>critical angle

5b) 51
5c) 30
5d) it totally internally reflects as angle of incidence is more than critical angle
5e) reflects away at same angle

6a) 90 out of phase
270 out of phase

6b) up, down to equilibrium, down again, back up to equilibrium
6c) it's transverse as longitudinal can't be polarised
6d)1.7 x10 to the 8
6e) 750
6f) was there any more questions here?

7a) light consists of a single wavelength
7b) lower intensity, wider fringes
7c) don't shine it into people's face or look along the beam as it will damage the eye
7d) central white maximum, subsidiary maxima consisting of spectra with blue on inside and red on outside of the fringes. The intensity is less than laser light.

I think I got 54/70 maybe. As I've taken time to create this could you give me yor opinions on my score?
5. (Original post by waheed786)
The Unofficial Mark scheme People.. thanks to Lebron! can everyone please find what's missing and where the last question goes so we can properly estimate what we got. Thanks
I got this maybe take the good bits from mine if there are any and add to yours? Also what do you think I would get /70 I'd greatly appreciate it if someone gave me their scores

My mark scheme

1a) square root of 1000 squared+ 6000 squared
1b) 32
1c) 9.2
1d) 3900000
1e) 22%

2a)0.55
2b) 240
2c) the horizontal displacement =ut. It takes the same time to falls and u is less and therefore the distance travelled is less

3a)
Inital quick acceleration shown by steep gradient
As it falls a drag force is produced
As the object falls the drag force on it increases reducing the resultant force
F=ma with respect to Newton's second law and so the acceleration decreases as it falls as shown by the gradient getting smaller
Eventually drag is equal and opposite to weight
Ball travels at constant Velocity shown by the straight part of the graph near the end of time
Reference to Newton's first law as it moves at a constant velocity as there is no resultant force
Some of the energy of the object is converted into internal energy of the oil
It finally hits the bottom as shown by the vertical line at the end

3b) I did a striaght line to about 3/4 the way up the line before it hit the fluid
Copied the graph from the page before for the second bit but starter it lower to show it's speed falls when it hits the oil
Striaght line at the end

4a) I got the wrong as I said f *proportional sign* KL and defined the terms
4b) 1200 n/m
4c) 9.4? I got this wrong I think I found how many squares there were and times by the area per square
4d) the object is permanently stretched and doesn't return to its inital length
4e) striaght line to the x axis but a bit to the right than the first list as there is extension at the end of unloading

5a) n1>n2
Angle of incidence>critical angle

5b) 51
5c) 30
5d) it totally internally reflects as angle of incidence is more than critical angle
5e) reflects away at same angle

6a) 90 out of phase
270 out of phase

6b) up, down to equilibrium, down again, back up to equilibrium
6c) it's transverse as longitudinal can't be polarised
6d)1.7 x10 to the 8
6e) 750
6f) was there any more questions here?

7a) light consists of a single wavelength
7b) lower intensity, wider fringes
7c) don't shine it into people's face or look along the beam as it will damage the eye
7d) central white maximum, subsidiary maxima consisting of spectra with blue on inside and red on outside of the fringes. The intensity is less than laser light.

I think I got 54/70 maybe. As I've taken time to create this could you give me yor opinions on my score?
6. can anyone remember how many marks the last question was worth?
7. (Original post by trentjoseph007)
JUST TO GET PEOPLES ATTENTION !!!

I think everyone misunderstood the last question on the paper. It was white light passing through a single slit. Look at the textbook page 202, figure 2. Apparently no one here realized it.

EDIT: It wasn't a easy question.
What does that mean?

Posted from TSR Mobile
8. Goodness me! Reckon I've got 55.. I wanted full UMS but that's not happening.. :l
9. (Original post by Aarongreatbanks)
I got this maybe take the good bits from mine if there are any and add to yours? Also what do you think I would get /70 I'd greatly appreciate it if someone gave me their scores

My mark scheme

1a) square root of 1000 squared+ 6000 squared
1b) 32
1c) 9.2
1d) 3900000
1e) 22%

2a)0.55
2b) 240
2c) the horizontal displacement =ut. It takes the same time to falls and u is less and therefore the distance travelled is less

3a)
Inital quick acceleration shown by steep gradient
As it falls a drag force is produced
As the object falls the drag force on it increases reducing the resultant force
F=ma with respect to Newton's second law and so the acceleration decreases as it falls as shown by the gradient getting smaller
Eventually drag is equal and opposite to weight
Ball travels at constant Velocity shown by the straight part of the graph near the end of time
Reference to Newton's first law as it moves at a constant velocity as there is no resultant force
Some of the energy of the object is converted into internal energy of the oil
It finally hits the bottom as shown by the vertical line at the end

3b) I did a striaght line to about 3/4 the way up the line before it hit the fluid
Copied the graph from the page before for the second bit but starter it lower to show it's speed falls when it hits the oil
Striaght line at the end

4a) I got the wrong as I said f *proportional sign* KL and defined the terms
4b) 1200 n/m
4c) 9.4? I got this wrong I think I found how many squares there were and times by the area per square
4d) the object is permanently stretched and doesn't return to its inital length
4e) striaght line to the x axis but a bit to the right than the first list as there is extension at the end of unloading

5a) n1>n2
Angle of incidence>critical angle

5b) 51
5c) 30
5d) it totally internally reflects as angle of incidence is more than critical angle
5e) reflects away at same angle

6a) 90 out of phase
270 out of phase

6b) up, down to equilibrium, down again, back up to equilibrium
6c) it's transverse as longitudinal can't be polarised
6d)1.7 x10 to the 8
6e) 750
6f) was there any more questions here?

7a) light consists of a single wavelength
7b) lower intensity, wider fringes
7c) don't shine it into people's face or look along the beam as it will damage the eye
7d) central white maximum, subsidiary maxima consisting of spectra with blue on inside and red on outside of the fringes. The intensity is less than laser light.

I think I got 54/70 maybe. As I've taken time to create this could you give me yor opinions on my score?
5e) I don't think total internal reflection occurs?
10. (Original post by AngryAsamoah)
can anyone remember how many marks the last question was worth?
3 marks?

Posted from TSR Mobile
11. (Original post by Aarongreatbanks)
My mark scheme

1a) square root of 1000 squared+ 6000 squared
1b) 32
1c) 9.2
1d) 3900000
1e) 22%

2a)0.55
2b) 240
2c) the horizontal displacement =ut. It takes the same time to falls and u is less and therefore the distance travelled is less

3a)
Inital quick acceleration shown by steep gradient
As it falls a drag force is produced
As the object falls the drag force on it increases reducing the resultant force
F=ma with respect to Newton's second law and so the acceleration decreases as it falls as shown by the gradient getting smaller
Eventually drag is equal and opposite to weight
Ball travels at constant Velocity shown by the straight part of the graph near the end of time
Reference to Newton's first law as it moves at a constant velocity as there is no resultant force
Some of the energy of the object is converted into internal energy of the oil
It finally hits the bottom as shown by the vertical line at the end

3b) I did a striaght line to about 3/4 the way up the line before it hit the fluid
Copied the graph from the page before for the second bit but starter it lower to show it's speed falls when it hits the oil
Striaght line at the end

4a) I got the wrong as I said f *proportional sign* KL and defined the terms
4b) 1200 n/m
4c) 9.4? I got this wrong I think I found how many squares there were and times by the area per square
4d) the object is permanently stretched and doesn't return to its inital length
4e) striaght line to the x axis but a bit to the right than the first list as there is extension at the end of unloading

5a) n1>n2
Angle of incidence>critical angle

5b) 51
5c) 30
5d) it totally internally reflects as angle of incidence is more than critical angle
5e) reflects away at same angle

6a) 90 out of phase
270 out of phase

6b) up, down to equilibrium, down again, back up to equilibrium
6c) it's transverse as longitudinal can't be polarised
6d)1.7 x10 to the 8
6e) 750
6f) was there any more questions here?

7a) light consists of a single wavelength
7b) lower intensity, wider fringes
7c) don't shine it into people's face or look along the beam as it will damage the eye
7d) central white maximum, subsidiary maxima consisting of spectra with blue on inside and red on outside of the fringes. The intensity is less than laser light.

I think I got 54/70 maybe. As I've taken time to create this could you give me yor opinions on my score?
12. (Original post by x-Sophie-x)
What does that mean?

Posted from TSR Mobile
Thats means its different form the double slit one, like most people r explaining.
13. Does anyone remember what was the question to... "5c) Speed of light in the object thing was1.7x10^8"
14. (Original post by waheed786)
Does anyone remember what was the question to... "5c) Speed of light in the object thing was1.7x10^8"
The answer was (3x10^8)/1.8 what ever that makes
15. (Original post by t-mister)
I think I got at least 50? How the hell did you get 35
16. (Original post by waheed786)
Does anyone remember what was the question to... "5c) Speed of light in the object thing was1.7x10^8"
and I think they gave you the refractive index as 1.8 or something
17. (Original post by Aarongreatbanks)
I think I got at least 50? How the hell did you get 35
I think some of the maths answers you gave are wrong i.e 1b, if I was you I'd fill out the re-sit form now and get in front of the queue. Better luck next time mate!!!!
18. (Original post by t-mister)
I think some of the maths answers you gave are wrong i.e 1b, if I was you I'd fill out the re-sit form now and get in front of the queue. Better luck next time mate!!!!
Haha you cocky bell
19. (Original post by .raiden.)
5e) I don't think total internal reflection occurs?
i agree, it does not happen, because between glass A and B it does since n1 > n2 and exceed its critical angle fo but when we worked out the critical angle r that section which we could work out to be 60 degrees since we have the angle of refraction from air to A. and by simply adding angles, you could find out at what angle it hit the boundary from A to C (which was less than the critical angle calculated hence it refracts and not T.I.R
20. (Original post by masryboy94)
i agree, it does not happen, because between glass A and B it does since n1 ^ n2 and exceed its critical angle fo but when we worked out the critical angle r that section which we could work out to be 60 degrees since we have the angle of refraction from air to A. and by simply adding angles, you could find out at what angle it hit the boundary from A to C (which was less than the critical angle calculated hence it refracts and not T.I.R
Do you agree that the incidence angle is 30 degrees? 90-60? Thank you

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