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# AQA Physics PHYA5 - 28th June 2016 [Exam Discussion Thread] watch

1. whats the super easy way of working out the number of moles of a gas as I seem to have forgotten?!
2. (Original post by Dann_a)
whats the super easy way of working out the number of moles of a gas as I seem to have forgotten?!
Pressure x Volume / Molar Gas Constant (8.31) x Temperature (in K)

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3. (Original post by Mango Milkshake)
Are fuel rods made of U235 or 238? Why doesn't fission work with 238?
I think U-235 is an unstable isotope because there are not enough neutrons, whilst U-238 is the most stable form of uranium?

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4. How is this question possible? For my answer of objective focal length I got 3.63m and eyepiece focal length 0.073m. This gives a magnification of 49.7 using M=fo/fe.

Would I get full marks for this answer? Mark scheme has different numbers, and is actually less accurate giving 48.6 using M=fo/fe

Hate AQA mark schemes and their stupid significant figures and rounding
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5. Does anyone doing Applied Physics have any notes that aren't the AQA textbook or antoine-education? I've read through those notes but I still don't know stuff when doing past papers
6. Hi Anyone doing applied 5c??

I could do with a bit of help of what to put on the six markers when it comes to flywheel questions
cheers
7. ASTROPHYSICS

Hi can anyone who does astrophysics tell me how/their method in drawing a diagram for a refracting telescope in normal adjustment please!!
8. Pretty much got my options unit down, but is anyone else here doing Turning Points? I'm having real issues with special relativity, and specifically, what 'Frame of Reference' really means, it seems to change throughout papers - or I have got myself a muddle.

Time dilation, for example. When looking at an explanation in my text book, I am told that a moving clock runs slower than a stationary clock. If T^0 < T, that would mean the time measured by the moving clock/probe/particle whatever, is the proper time, T0. However, when asked to work out the 'time taken in the proton's frame of reference' often the mark scheme is working out t?

Taken from the text book here, For example, the half-life of muons at rest is 1.5 s. A beam of muons travelling at 99.6% of thespeed of light (v = 0.996c) would therefore decay to 50% of its initial intensity in a distance of450 m (= 0.996c × 1.5 s) in their own frame of reference. Which means the smaller time t0 is in the muons frame of reference.
But then, when asked this in the June 2011 paper -
In an experiment, a beam of protons moving along a straight line at a constant speed of1.8 × 108m s–1 took 95 ns to travel between two detectors at a fixed distance d0 apart. Asshown in Figure 5.
Calculate the distance between the two detectors in the frame of reference of theprotons.
The mark scheme intends for you to work out d. So in the moving frame of reference, the length is not the proper length, but the time is the proper time?

I hope someone can answer this, it leads me to thinking far too much when answering these questions! I hope we get a lovely one about mass and energy because they're fine!
9. can someone explain the P=AE formula to me from the radioactive section. Just saw it in my notes but dont see why it would be relevant with radioactive decay
10. (Original post by boyyo)
can someone explain the P=AE formula to me from the radioactive section. Just saw it in my notes but dont see why it would be relevant with radioactive decay
power= E/t
W= J/s
and the activity is the number of nuclei that decay per second so the unit would be s^-1
J*s^-1= W so P=AE
11. (Original post by ssel17)
Pretty much got my options unit down, but is anyone else here doing Turning Points? I'm having real issues with special relativity, and specifically, what 'Frame of Reference' really means, it seems to change throughout papers - or I have got myself a muddle.

Time dilation, for example. When looking at an explanation in my text book, I am told that a moving clock runs slower than a stationary clock. If T^0 < T, that would mean the time measured by the moving clock/probe/particle whatever, is the proper time, T0. However, when asked to work out the 'time taken in the proton's frame of reference' often the mark scheme is working out t?

Taken from the text book here, For example, the half-life of muons at rest is 1.5 s. A beam of muons travelling at 99.6% of thespeed of light (v = 0.996c) would therefore decay to 50% of its initial intensity in a distance of450 m (= 0.996c × 1.5 s) in their own frame of reference. Which means the smaller time t0 is in the muons frame of reference.
But then, when asked this in the June 2011 paper -
In an experiment, a beam of protons moving along a straight line at a constant speed of1.8 × 108m s–1 took 95 ns to travel between two detectors at a fixed distance d0 apart. Asshown in Figure 5.
Calculate the distance between the two detectors in the frame of reference of theprotons.
The mark scheme intends for you to work out d. So in the moving frame of reference, the length is not the proper length, but the time is the proper time?

I hope someone can answer this, it leads me to thinking far too much when answering these questions! I hope we get a lovely one about mass and energy because they're fine!
Turning points here also, I wish I could answer your question but this is often where I trip up. I have a very hard time understanding what frame of reference to use.
12. for specific heat capacity and other calculations is temperature done in Kelvins or Celsius?
13. I'm really struggling with turning points, can anyone recommend any websites/videos that they have found to be useful?
14. (Original post by Dann_a)
for specific heat capacity and other calculations is temperature done in Kelvins or Celsius?
Kelvin, the units of specific heat are in JK^-1mol^-1 (
15. (Original post by Abc321zxc)
I'm really struggling with turning points, can anyone recommend any websites/videos that they have found to be useful?
What parts of turning points are you struggling with?
16. (Original post by ssel17)
Pretty much got my options unit down, but is anyone else here doing Turning Points? I'm having real issues with special relativity, and specifically, what 'Frame of Reference' really means, it seems to change throughout papers - or I have got myself a muddle.

Time dilation, for example. When looking at an explanation in my text book, I am told that a moving clock runs slower than a stationary clock. If T^0 < T, that would mean the time measured by the moving clock/probe/particle whatever, is the proper time, T0. However, when asked to work out the 'time taken in the proton's frame of reference' often the mark scheme is working out t?

Taken from the text book here, For example, the half-life of muons at rest is 1.5 s. A beam of muons travelling at 99.6% of thespeed of light (v = 0.996c) would therefore decay to 50% of its initial intensity in a distance of450 m (= 0.996c × 1.5 s) in their own frame of reference. Which means the smaller time t0 is in the muons frame of reference.
But then, when asked this in the June 2011 paper -
In an experiment, a beam of protons moving along a straight line at a constant speed of1.8 × 108m s–1 took 95 ns to travel between two detectors at a fixed distance d0 apart. Asshown in Figure 5.
Calculate the distance between the two detectors in the frame of reference of theprotons.
The mark scheme intends for you to work out d. So in the moving frame of reference, the length is not the proper length, but the time is the proper time?

I hope someone can answer this, it leads me to thinking far too much when answering these questions! I hope we get a lovely one about mass and energy because they're fine!
Okay, I'm going to explain this as my teacher explained it to me. I don't know if this will help but it did for me. Now Imagine each moun in the beam as a person, lets name him Bob and he is in a box wearing a watch and he is unable to see the outside world. As Bob is travelling near the speed of light he looks at his watch and time is stationary/normal because to him everything around him is normal/stationary. Now imagine another person observing Bob traveling at this speed and is able to see his watch. Because a moving clock look runs slower than a stationary clock the observer would have a dilated time compared to Bob. And so the dilated time would be the time that the observer would be viewing whilst the proper time is the time of when bob sees his watch.

So in the June 2011 paper, the time that took the protons to travel between the two detectors was measured by a person observing the protons and so it is the dilated time rather than the proper time.

I hoped this helped. I am not really good at explaining things.
17. (Original post by Protoxylic)
Kelvin, the units of specific heat are in JK^-1mol^-1 (
Was it different in june 2010 then?
I thought it was kelvins and then on the mark scheme it was done in celcius so i got everything wrong?
18. (Original post by Dann_a)
Was it different in june 2010 then?
I thought it was kelvins and then on the mark scheme it was done in celcius so i got everything wrong?
Link the question, I did this exam last year so I don't quite remember questions from specific papers
19. (Original post by Protoxylic)
What parts of turning points are you struggling with?
Michelson–Morley experiment
20. (Original post by ssel17)
Pretty much got my options unit down, but is anyone else here doing Turning Points? I'm having real issues with special relativity, and specifically, what 'Frame of Reference' really means, it seems to change throughout papers - or I have got myself a muddle.

Time dilation, for example. When looking at an explanation in my text book, I am told that a moving clock runs slower than a stationary clock. If T^0 < T, that would mean the time measured by the moving clock/probe/particle whatever, is the proper time, T0. However, when asked to work out the 'time taken in the proton's frame of reference' often the mark scheme is working out t?

Taken from the text book here, For example, the half-life of muons at rest is 1.5 s. A beam of muons travelling at 99.6% of thespeed of light (v = 0.996c) would therefore decay to 50% of its initial intensity in a distance of450 m (= 0.996c × 1.5 s) in their own frame of reference. Which means the smaller time t0 is in the muons frame of reference.
But then, when asked this in the June 2011 paper -
In an experiment, a beam of protons moving along a straight line at a constant speed of1.8 × 108m s–1 took 95 ns to travel between two detectors at a fixed distance d0 apart. Asshown in Figure 5.
Calculate the distance between the two detectors in the frame of reference of theprotons.
The mark scheme intends for you to work out d. So in the moving frame of reference, the length is not the proper length, but the time is the proper time?

I hope someone can answer this, it leads me to thinking far too much when answering these questions! I hope we get a lovely one about mass and energy because they're fine!
Proper time is defined as the frame that experiences the smallest possible time interval and is the frame for which the person/thing/object is present at both events. E.g a muon travelling between points A and B is present in it's own frame at the origin at both points A and B and thus the muon and it's frame experience proper time - all other time intervals are longer including the observer. So in this case the muon experiences proper time.

The protons experience proper time and also a contracted length for points A and B defined as the edges of the detector, i.e the detector length is shorter in their frame compared to the lab frame.

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