AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread]

Original post by CD223

[br]\Delta Q = mc \Delta T[br]

[br]c = \dfrac{\Delta Q}{m \Delta T}[br]

[br]\Delta Q = 7.5 \times 10^4 - 3.0 \times 10^4[br]

[br]\therefore c = \dfrac{7.5 \times 10^4 - 3.0 \times 10^4}{1.2 \times (327-84)}[br]

[br]\therefore c = 155 Jkg^{-1}K^{-1}[br]

Why is the change in temperature 327-84? Kind of confused

Reply 1883

Original post by Protoxylic

Basically dt is not the true time duration of each collision, it is the time between collisions which requires the assumption that the time duration of each collision is small.

That makes perfect sense but do you not think assuming that would give us the wrong overall pressure?

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Reply 1884

Protoxylic

14

Original post by Mehrdad jafari

That makes perfect sense but do you not think assuming that would give us the wrong overall pressure?

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The pressure is of the order of KPa normally, so this assumption is justified by the fact that the difference between the actual pressure and the calculated pressure isn't that much I presume

Reply 1885

SuperMushroom

9

Original post by Protoxylic

Offer holder for NatSci at Cambridge :colondollar:

. My passion is in Chemistry, however. But (grades permitting) I get to continue with Physics, Chem, Maths and take up Material Sciences at Cambridge :tongue:

Ahh awesome!! Well all the best hopefully you get in

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Reply 1886

JJBinn

Do any of you guys know why 1c uses the change in temperature as 327-84? http://filestore.aqa.org.uk/subjects/AQA-PHYA51-W-QP-JUN10.PDF

Reply 1887

ubisoft

3

Just started revision for this. How likely is it to get A* after a day's revision?

Reply 1888

Original post by Protoxylic

The pressure is of the order of KPa normally, so this assumption is justified by the fact that the difference between the actual pressure and the calculated pressure isn't that much I presume

Well, that's true, we tend to give the priority to the experimental observations rather than the theoretical understanding of it.

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Reply 1889

Protoxylic

14

Original post by SuperMushroom

Ahh awesome!! Well all the best hopefully you get in

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Cheers! And I hope you get the grades you need for wherever you want to go :smile:

Reply 1890

gcsestuff

Absolutely bricking it! I know the spec inside out I can just tell its gonna be a bad exam

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Reply 1891

gcsestuff

Someone ask me some turning point questions

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Reply 1892

CD223

OP

10

Original post by JJBinn

Why is the change in temperature 327-84? Kind of confused

Because that's the temperature that the mould decreases to, from its initial temperature of 327 degrees.

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Reply 1893

Original post by ubisoft

Just started revision for this. How likely is it to get A* after a day's revision?

Just how likely you think it is :smile:

Reply 1894

ubisoft

3

Original post by Mehrdad jafari

Just how likely you think it is :smile:

How likely do I think it is?

Reply 1895

Original post by gcsestuff

Someone ask me some turning point questions

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ether, a hypothetical medium once thought to necessary to support the propagation of electromagnetic waves throughout space, cannot explain why a light shone towards a detector on a moving train traveling in the same direction as the incident light takes the same amount of time to reach the detector as if the train was stationary. Explain why :smile: