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AQA Physics PHYA4 - Thursday 11th June 2015 [Exam Discussion Thread] watch

1. (Original post by gcsestuff)
I agree, some questions I just look at and I have no idea how to start them, so they take a bit more thinking about. With multiple choice least you always know where to start and you can always get rid of a few answers

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Exactly. Looking at the answers is so much easier than trying to come up with them haha.

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2. (Original post by CD223)
Well here are the boundaries:
Attachment 414267

Which suggest that's false, given the first section is 25 marks.

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http://filestore.aqa.org.uk/over/sta...-JUNE-2014.PDF

Any idea what those second grey grade boundaries suggest?
3. (Original post by muyiwaaiyenuro)
http://filestore.aqa.org.uk/over/sta...-JUNE-2014.PDF

Any idea what those second grey grade boundaries suggest?
They're the individual sections' breakdown I guess. Even though your grade is actually worked out by the sum total of your marks.

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4. Can someone help me with question 13 please?http://filestore.aqa.org.uk/subjects...1-QP-JUN14.PDF
Can someone help me with question 13 please?http://filestore.aqa.org.uk/subjects...1-QP-JUN14.PDF

This means
.

The original distance was when the force was .

The force is halved to become , so the previous distance must be .

Does that help?

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6. (Original post by CD223)

This means
.

The original distance was when the force was .

The force is halved to become , so the previous distance must be .

Does that help?

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Sorry to bother you more, but where does the root 2 come from?
My brain doesn't seem to be working with me haha!
Sorry to bother you more, but where does the root 2 come from?
My brain doesn't seem to be working with me haha!
As you have:

On one side of the equation, you must have

On the other side - does that make sense?

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8. How would you go about mathematically proving this?

I got it right by guessing, because:

But this gives the inverse of the correct answer?

I know KE depends on m as well as v, but I just didn't think enough info was given in the question about the velocity? It just says the initial velocity is U, then it coalesces with a stationary object, without saying the velocity after?

Confused.

9. EDIT: Never mind! All sorted

The frequency has to reduce by two thirds so

So the period would have to increase by 1.5, so

As

This means m would have to increase by 1.5 squared so

meaning 0.50kg needs to be added.
10. (Original post by Mehrdad jafari)
Use this equation as this is quicker and less stressful in the exam
Attachment 414673

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Edit: oops, in the first equation its K/m and not m/k

Thanks

Do you get the KE question?
I just didn't think there was enough info on the velocity

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11. http://filestore.aqa.org.uk/subjects...W-QP-JAN10.PDF Question 11 Lads, I can't seem to get my head around where to start off

EDIT: No problem just got it by forming an equation of the earths GFS and another for the planets GFS, rearranging both so M = blah blah and dividing the pair to get X^2Y. Just wondering if there would be any quicker method or realizing some sort of ratio without having to do all of that?
12. (Original post by Mehrdad jafari)
In case if you haven't got it

Attachment 414675

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Great! Thank you really should have got that one >.<

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13. (Original post by lebanon95)
http://filestore.aqa.org.uk/subjects...W-QP-JAN10.PDF Question 11 Lads, I can't seem to get my head around where to start off

EDIT: No problem just got it by forming an equation of the earths GFS and another for the planets GFS, rearranging both so M = blah blah and dividing the pair to get X^2Y. Just wondering if there would be any quicker method or realizing some sort of ratio without having to do all of that?
Unfortunately that method is the quickest way I know of. Form an equation for M:

Then sub in the values x and y, and divide.

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14. (Original post by CD223)
As you have:

On one side of the equation, you must have

On the other side - does that make sense?

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Sorry it still doesn't, I don't see where the root 2 comes from.
I don't know how I don't get it!
Sorry it still doesn't, I don't see where the root 2 comes from.
I don't know how I don't get it!
F is is inversely proportional to the distance, d, squared. This means that, if you look at it another way:

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16. Not sure on why the angular velocity is the same. Using w=v/r means that if the radius is smaller the speed should be greater??

Or am I supposed to be using the g=f/m. Which shows acceleration only depends on force and mass of the object.

Thanks again 😀😀

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17. (Original post by CD223)
F is is inversely proportional to the distance, d, squared. This means that, if you look at it another way:

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Thank you so much! Seriously thank you!

Looking at it like that I understand it!
18. (Original post by gcsestuff)

Not sure on why the angular velocity is the same. Using w=v/r means that if the radius is smaller the speed should be greater??

Or am I supposed to be using the g=f/m. Which shows acceleration only depends on force and mass of the object.

Thanks again 😀😀

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Both points X and Y turn through the same angle in the same time period. (360 degrees or radians in 24 hours).

As:

This means that both points undergo the same angular displacement, theta, in the same time. They therefore have the same angular velocity.

NB: They will have different linear velocities, however.

With regards to the potential of both points,

because

And .

Does that make sense?

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Thank you so much! Seriously thank you!

Looking at it like that I understand it!
No worries gotta love a confusing ratio question from AQA -.-

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20. (Original post by CD223)
No worries gotta love a confusing ratio question from AQA -.-

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AQA are just the best (¬_¬)

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