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Oxford Physics: PAT test discussion

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Original post by Electric-man7
Guys what was the solution to the refraction index question, and the one about the minimum displacement of one of the blocks connected by an elastic spring, oh and the integration one? You know what never mind GIVE ME ALL THE SOLUTIONS.

Forgot what the actual solution to the refractive index one is but you have to find the apparent depth (the straight line your eye draws into the water from the refracted ray) of the ring when it gets to the bottom. Distance between areas of zero sound for the waves question was (lambda1lambda2)/lambda+lambda2
(edited 6 years ago)
Okay, but was the height of the eye constant for the refractive index question?
Original post by Electric-man7
Okay, but was the height of the eye constant for the refractive index question?


For the question about the binary bodies, I made the stupid mistake of taking the gravitational force from the center of orbit, instead of the distance between the stars, ie I should have got a final ration of sqrt2/2 but I messed up, how many marks will i lose, I am disappointed because had I paid more attention, I would have easily got tose 9 marks
Original post by Electric-man7
Okay, but was the height of the eye constant for the refractive index question?


I did assume that but dont know if thats correct
Original post by Electric-man7
Okay, but was the height of the eye constant for the refractive index question?


Don't see why not from what I saw the eye stays at the exact same position and looks at the same position in the liquid they would've mentioned otherwise
It changes the solution quite drastically I believe. There were 5 marks for the length of displacement of a block, what was your solution? My anser only has like 2 or three steps so it seems fishy.
Original post by Electric-man7
It changes the solution quite drastically I believe. There were 5 marks for the length of displacement of a block, what was your solution? My anser only has like 2 or three steps so it seems fishy.


Considering it was given in the diagram and they just wanted an expression for the depth and not an actual number its pretty safe to assume that the height is constant and that it can be used in the final solution. Forgot but I think it's the same as everyone else I just resolved force of the spring and the frictional forcd
So was your final answer mgu/k?
And what do you mean by resolve were they not on a horizontal plane?
Original post by Electric-man7
For the question about the binary bodies, I made the stupid mistake of taking the gravitational force from the center of orbit, instead of the distance between the stars, ie I should have got a final ration of sqrt2/2 but I messed up, how many marks will i lose, I am disappointed because had I paid more attention, I would have easily got tose 9 marks


I did the same if u wrote the solutions p clearly not too many (probably 1-3)
Original post by Electric-man7
So was your final answer mgu/k?


Yea think so sorry not resolve just equate
Oh thats a relief, Its just that it basically introduces another layer of triginometry (cosine rule) which I was told would be worth like 4 marks, and so anet loss of 5 marks for such a silly oversight. The integral question was too easy provided you knew the insight right?
Original post by Electric-man7
Oh thats a relief, Its just that it basically introduces another layer of triginometry (cosine rule) which I was told would be worth like 4 marks, and so anet loss of 5 marks for such a silly oversight. The integral question was too easy provided you knew the insight right?

I did it by splitting it into right angled triangles so no cosine rule needed. Didn't manage to do the integral question didn't think u cld treat t as a constant in the integral
Original post by joe.lai
I did the same if u wrote the solutions p clearly not too many (probably 1-3)


I also made the same mistake:frown:
Original post by joe.lai
I did it by splitting it into right angled triangles so no cosine rule needed. Didn't manage to do the integral question didn't think u cld treat t as a constant in the integral


Why not as a constant? If it would be an area dependent of t then you can differentiate that area with respect to t while t is not a funtion of anything just a variable
Ahh, I am glad that preparing for STEP, helped me make short work of the problem. The circle geometry had me crying, in the end I got some value which a person taking the exam with told me was wrong (sqrt 69). Possible the most diffcult pat exam do this date If I am honest. The MCQ's for math were surprisingly harder than physics.
Original post by Tomyil12345
Why not as a constant? If it would be an area dependent of t then you can differentiate that area with respect to t while t is not a funtion of anything just a variable


No clue mate probs should've done it considering I had nothing else to do but I think I was focusing too much on the physics questions which I know I'm slightly better at so just kind of ignored it
Original post by Electric-man7
Ahh, I am glad that preparing for STEP, helped me make short work of the problem. The circle geometry had me crying, in the end I got some value which a person taking the exam with told me was wrong (sqrt 69). Possible the most diffcult pat exam do this date If I am honest. The MCQ's for math were surprisingly harder than physics.


I quite liked them tot some of the mcq questions tested you're understanding quite well like the pulleys and electron momentum questions
Original post by Tomyil12345
Why not as a constant? If it would be an area dependent of t then you can differentiate that area with respect to t while t is not a funtion of anything just a variable


He is trying to say that he didn't realise you could do that, not saying that t couldn't be treated as a constant.
Can someone explain the circle question? What was the final answer?

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