HSC Physics Marathon 2013-2015 Archive (2 Viewers)
- Thread starter Magical Kebab
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re: HSC Physics Marathon Archive
Split ring reverses current every half cycle to maintain the rotation of the motor in the same direction, slip ring rotates with the coil and maintains electrical contact
re: HSC Physics Marathon Archive
meeeeee just got up to astro in the past paper i'm doing
re: HSC Physics Marathon Archive
my bad, For AC power generation, a generator consists of slip rings which rotate as the armature coil rotates. Since there is contact with the brushes throughout the whole rotation of the armature coil, current is induced in both directions, hence producing an alternating current. For DC power generation, a generator has a split ring commutator which operates similar to that of a motor’s commutator – ensures that current only travels in one direction, hence producing a direct current
astroman
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re: HSC Physics Marathon Archive
Can u tell me what filters are used for in observing stars? I honestly have no idea.
godofindolence
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re: HSC Physics Marathon Archive
what did you get for the answer? iirc I got 30.1 or 30.2 or something that rounded down to 30
re: HSC Physics Marathon Archive
I got 30.05 when I did it, no complicated simultaneous equations lol
godofindolence
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Gravitational potential energy is a measure of the amount of energy required to bring an object from a point of infinity into a point within a gravitational field. A change is gravitational potential energy therefore measures the work done in order to physically move the object. At a point of infinity, the GPE of an object is obviously 0, and as it approaches the gravitational field, GPE is lost, and instead being converted to KE, thus, it follows that GPE is negative.
Drsoccerball
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When observing a star with our eyes the colour green becomes easier to see than other colours as our eyes are more sensitive to green. Furthermore devices such as photographic film are sensitive to the blue colour. Therefore in order to find a compromise and actually discover which one is "actually" brighter we use filters. We do the B-V where B is the blue colour and V is the green in order to develop a colour spectrum. This allows us to understand to what extent a star is blue or green. (The more negative the star is the more blue it is) Furthermore the use of this colour spectrum can allow us to get a "unbias" reading for the apparent magnitude of a star. We can then use this new information in tandem with the HR diagram to find the absolute magnitude more accurately.
godofindolence
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Filters can also be used to determine the black body curve using the methods above. Black body curve is obviously really helpful because it allows us to determine temperature and class etc.
Well filters can be used to determine the colour index of the stars. This is done by viewing them through blue and yellow filters. A large main sequence star (O and B class for example) is more blue in colour and therefore have a much lower apparent blue magnitude compared to yellow. This means that its colour index (B-V) is far lower than that of a G and K class stars. This colour index corresponds accurately with the position of a star on the H-R diagrams and allow for easy and quick classification of stars.
Filters can also be used to determine the black body curve using the methods above. Black body curve is obviously really helpful because it allows us to determine temperature and class etc.
re: HSC Physics Marathon Archive
You should have a read of mrreditor's astro notes he posted in the astro section, they're gun as
(too slow lol)
I assume you're referring to B-V index (same principle applies to all filters). A blue filter allows for only light in the blue part of the spectrum, this is the 'blue magnitude' (B), a visual filter allows only light from the yellow-green portion of the spectrum -- known as the visual magnitude (V). Eg, when a blue star is observed through a blue filter it will appear bright, and conversely will appear dull when seen through a visual filter. Meaning its blue magnitude will be small and visual magnitude will be large (keeping in mind the smaller or more negative the value the brighter it is), the B-V index is essentially the difference between the blue and visual magnitude, meaning that a blue star will have a more negative value (or smaller). Vice versa, a yellow/red/orange star will have a less negative value (or larger). By using the B-V index astronomers can determine the surface temp of stars, since hotter stars a blue and cooler stars are red, it can also determine the spectral class etc. Other filters and indexes can be used, not just B, V.
You should have a read of mrreditor's astro notes he posted in the astro section, they're gun as
(too slow lol)
Mathsisfun15
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re: HSC Physics Marathon Archive
twins paradox isn't even in the syllabus
twins paradox isn't even in the syllabus
Mathsisfun15
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For the quanta to quarks folk
Theories and experiments not only help increase our understanding but also generate new questions.
Use the standard model of matter to support this statement.
6 marks
For the quanta to quarks folk
Theories and experiments not only help increase our understanding but also generate new questions.
Use the standard model of matter to support this statement.
6 marks
Mathsisfun15
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re: HSC Physics Marathon Archive
Events that are simultaneous in one frame of reference are not necessarily simultaneous when viewed from a different frame of reference
re: HSC Physics Marathon Archive
But what does it demonstrate?
That's what the relativity of simultaneity is
But what does it demonstrate?
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