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Edexcel A2 Physics Unit 5 'Physics from Creation to Collapse' watch

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    (Original post by yadas)
    Without damping this specific frequency is natural frequency of the oscillating system, obviously.
    Damping reduces the frequency at which maximum amplitude is possible.
    Increasing damping further reduces this frequency, as you can see from the picture.
    Thought the maximum energu would still be absorbed at natural frequency, even with damping.


    Are you taking the fourth root of T4?
    Using L = 2.8*1026, A = 5.5*1018 and σ = 5.67*10-8, gives a value of T4 as 8.93*1014.
    The fourth root of that is about 5470K.
    (5800 - 5470 = 330, can be rounded to 300.)
    gah, dont know wth i was doing!

    Again-thank you =]
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    (Original post by yadas)
    1.Without damping this specific frequency is natural frequency of the oscillating system, obviously.
    2.Damping reduces the frequency at which maximum amplitude is possible.
    3.Increasing damping further reduces this frequency, as you can see from the picture.
    4.Thought the maximum energu would still be absorbed at natural frequency, even with damping.
    The graph you linked refers to transmissibility of energy. Your second point is confusing me - surely, with reference to your graph, maximum amplitude is always possible when the system isnt too heavily damped because as long as some transmission is ocurring the amplitude will be increasing so the frequency isnt relevant? Confused...
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    (Original post by JayAyy)
    I understand everything except for SHM
    it's not that difficult, you just need to understand its concept, it's defined as a harmonic motion where the frequency is independant of the amplitude, and the restoring force is directed towards the central point of the motion. In SHM oscillating systems, the force is directly proportional to the distance, relating F and x as in Hooke's law F= -kx.

    F= -kx = ma
    so a = -kx / m

    memorize the equations, they all relate to each other!
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    (Original post by Bronze92)
    it's not that difficult, you just need to understand its concept, it's defined as a harmonic motion where the frequency is independant of the amplitude, and the restoring force is directed towards the central point of the motion. In SHM oscillating systems, the force is directly proportional to the distance, relating F and x as in Hooke's law F= -kx.

    F= -kx = ma
    so a = -kx / m

    memorize the equations, they all relate to each other!
    I know about it, it's just the kind of questions that come up that catch me off guard.
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    (Original post by lefneosan)
    The graph you linked refers to transmissibility of energy. Your second point is confusing me - surely, with reference to your graph, maximum amplitude is always possible when the system isnt too heavily damped because as long as some transmission is ocurring the amplitude will be increasing so the frequency isnt relevant? Confused...
    That graph is a bit more complicated than we should know for this exam. Try this one.
    As you can see the peak amplitude possible for each damping is shifted to the left (lower frequency).
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    do we need to know about escape velocity
    ?
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    (Original post by yadas)
    That graph is a bit more complicated than we should know for this exam. Try this one.
    As you can see the peak amplitude possible for each damping is shifted to the left (lower frequency).
    k thanks
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    (Original post by kappleberry)
    do we need to know about escape velocity
    ?
    no, it's not included in the syllabus.
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    (Original post by Bronze92)
    no, it's not included in the syllabus.
    yay. =]



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    http://cid-5432f573d3fc3f5a.office.l...energy%20A.doc

    Could someone help with Q7, c(ii).

    Im not at all good with these ratio Qs! grr
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    Also..what practicals do we need to know?
    Do we need to know the setup for experiment to find relationship between pressure of gas and temp.
    I know I should check in the spec, but wanna b sure..!
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    (Original post by kappleberry)
    Also..what practicals do we need to know?
    Do we need to know the setup for experiment to find relationship between pressure of gas and temp.
    I know I should check in the spec, but wanna b sure..!
    I checked the syllabus and compared it to the teacher's guidance book, these are the ones that are included for unit 5:

    -Specific heat capacity of a liquid / solid
    -Pressure and Temperature
    -Pressure and Volume
    (just in case, study the experiment relating the volume and the temperature although it's not included in the syllabus)
    -Measuring the activity of a radioactive source
    -Simulation of a radioactive decay (dice)
    -SHM experiment
    -Forced oscillations
    -Investigating damped oscillations

    =) Good luck!
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    (Original post by kappleberry)
    yay. =]



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    http://cid-5432f573d3fc3f5a.office.l...energy%20A.doc

    Could someone help with Q7, c(ii).

    Im not at all good with these ratio Qs! grr
    I basically calculated the mass of air at 227 degrees (as you did in part (i)) and then the density using m/v of each.
    Then you put the density at 227/27, which should give you around 0.6.
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    how is the fate of the universe associated with hubble's constant? (i dont understand what the mark scheme says for this in the specimen paper!) - its questions 15 btw x
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    (Original post by Bronze92)
    I checked the syllabus and compared it to the teacher's guidance book, these are the ones that are included for unit 5:

    -Specific heat capacity of a liquid / solid
    -Pressure and Temperature
    -Pressure and Volume
    (just in case, study the experiment relating the volume and the temperature although it's not included in the syllabus)
    -Measuring the activity of a radioactive source
    -Simulation of a radioactive decay (dice)
    -SHM experiment
    -Forced oscillations
    -Investigating damped oscillations

    =) Good luck!
    GAAH, thannk yuuuu
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    (Original post by kappleberry)
    http://cid-5432f573d3fc3f5a.office.l...energy%20A.doc

    Could someone help with Q7, c(ii).

    Im not at all good with these ratio Qs! grr
    From pV = NkT, V/T = Nk/p, where Nk/p is constant (N - number of molecues in the oven is constant, they dont open the oven and leave, p is at atmospheric pressure as they stated, k is constant on its own).
    Hence V1/T1 = V2/T2. (1)
    (Using 1 for 27°C and 2 for 227°C)
    As density, ρ = m/V, V = m/ρ.
    Substituting this into (1) gives:
    m/ρ1T1 = m/ρ2T2
    As mass is constant:
    ρ1T1 = ρ2T2
    We need the ratio of ρ21 (at 227° to 27°C).
    ρ21 = T1/T2 = (272+27)/(273+227) = 300/500 = 0.6.

    (Original post by kappleberry)
    Also..what practicals do we need to know?
    Do we need to know the setup for experiment to find relationship between pressure of gas and temp.
    I know I should check in the spec, but wanna b sure..!
    I think the suggested experiments from the syllabus would be sufficient. :yes:
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    (Original post by helooo19x)
    how is the fate of the universe associated with hubble's constant? (i dont understand what the mark scheme says for this in the specimen paper!) - its questions 15 btw x
    Hubble's law states that the recessional velocity of a galaxy away from us is directly proportional to its distance away. This means that the Hubble constant implies that the Universe is expanding. However, the density of the Universe is constantly changing due to the expansion and also gravitational forces between galaxies. Since the expansion is not constant, neither is Hubble's "constant", so we are very uncertain about how our Universe will end up.
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    (Original post by yadas)
    From pV = NkT, V/T = Nk/p, where Nk/p is constant (N - number of molecues in the oven is constant, they dont open the oven and leave, p is at atmospheric pressure as they stated, k is constant on its own).
    Hence V1/T1 = V2/T2. (1)
    (Using 1 for 27°C and 2 for 227°C)
    As density, ρ = m/V, V = m/ρ.
    Substituting this into (1) gives:
    m/ρ1T1 = m/ρ2T2
    As mass is constant:
    ρ1T1 = ρ2T2
    We need the ratio of ρ21 (at 227° to 27°C).
    ρ21 = T1/T2 = (272+27)/(273+227) = 300/500 = 0.6.


    I think the suggested experiments from the syllabus would be sufficient. :yes:
    For the ratio one, I just found the densities and ratioed them, got the right answer. < Is that right, though?
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    (Original post by Bronze92)
    I checked the syllabus and compared it to the teacher's guidance book, these are the ones that are included for unit 5:

    -Specific heat capacity of a liquid / solid
    -Pressure and Temperature
    -Pressure and Volume
    (just in case, study the experiment relating the volume and the temperature although it's not included in the syllabus)
    -Measuring the activity of a radioactive source
    -Simulation of a radioactive decay (dice)
    -SHM experiment
    -Forced oscillations
    -Investigating damped oscillations

    =) Good luck!
    thanks for that. What do you mean by dice?
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    (Original post by unamed)
    For the ratio one, I just found the densities and ratioed them, got the right answer. < Is that right, though?
    Yeah, of course.
    Again, there are many ways of solving physics in A2.
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    Can someone explain to me what a supernova is and how they are formed?

    Also, I don't understand how the properties of a Cepheid variable relate to its Intensity/Time graph. Why will a more luminous Cepheid variable have a greater period of pulsation?
 
 
 
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