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STEP Prep Thread 2016 (Mark. II)

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Zacken
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Original post by Themathgeek
Could someone please explain this in pm?

I don't understand how T= what they have given is when the horizontal velocity is 0. How do you figure that out?

Thanks
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I don't really understand what you're asking, could you clarify?
If there's a question that says to prove 2 things are necessary and sufficient (if and only if ect.) and you prove that one thing is necessary for the other and everything you've done is reversible, is there some easy way of showing/stating this without physically having to do everything in reverse?
Original post by smartalan73
If there's a question that says to prove 2 things are necessary and sufficient (if and only if ect.) and you prove that one thing is necessary for the other and everything you've done is reversible, is there some easy way of showing/stating this without physically having to do everything in reverse?


Double ended arrows between each line of working.
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Original post by smartalan73
If there's a question that says to prove 2 things are necessary and sufficient (if and only if ect.) and you prove that one thing is necessary for the other and everything you've done is reversible, is there some easy way of showing/stating this without physically having to do everything in reverse?


Like so:   ⟺  \iff

Although you'd be expected to make an explicit statement at the end that every step is reversible just to be safe.
Just to make sure, when drawing a graph, are there some features that must be find like asymptotes, stationary points, points that cross x, y axis , symmetry or it really depends on the question? And sketch and draw I guess they are the same no? Sorry if the question is a bit silly.:smile:
Original post by Geraer100
Just to make sure, when drawing a graph, are there some features that must be find like asymptotes, stationary points, points that cross x, y axis , symmetry or it really depends on the question? And sketch and draw I guess they are the same no? Sorry if the question is a bit silly.:smile:


I think you always need to show where the asymptotes are, and roughly where stationary points and axis crossings are (i.e. which quadrant). Generally if you need to calculate stationary point coordinates I think it will tell you. I'd say sketch and draw are pretty much the same, although sometimes sketch means a really quick sketch, whereas draw usually involves a bit more detail.
Original post by Zacken
I don't really understand what you're asking, could you clarify?


Sorry I just realised how unclear that was

How do you know that the horizontal velocity is 0 when T= Ucostheta/(kg) ?

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Original post by sweeneyrod
I think you always need to show where the asymptotes are, and roughly where stationary points and axis crossings are (i.e. which quadrant). Generally if you need to calculate stationary point coordinates I think it will tell you. I'd say sketch and draw are pretty much the same, although sometimes sketch means a really quick sketch, whereas draw usually involves a bit more detail.


Okay, thanks! I guess that the equation which I need to solve to find the stationary points or axis crossing maybe also matters when come to if the coordinates need to be stated.
Original post by Zacken
20 paged booklet of standard lined paper and then as many additional 5 paged lined booklet as you want. No blank paper. All graphs are done on the lined paper in the booklet.

You can ask for rough blank paper that won't get marked, but don't, there's no point to it. Do all your working in the booklet.



Well done!


Only reason I can think of that I would ask for spare unmarked paper is when I am proving a condition one way, but I want to start in reverse, so I do the reverse calculations on a rough sheet then put them the right way on the actual answer booklet (and that way the examiner doesn't think bad of you). Can we do this in the exam?


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Original post by jjsnyder
Only reason I can think of that I would ask for spare unmarked paper is when I am proving a condition one way, but I want to start in reverse, so I do the reverse calculations on a rough sheet then put them the right way on the actual answer booklet (and that way the examiner doesn't think bad of you). Can we do this in the exam?


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I do that many times ( idk if it's wrong)

P <= Q <= R ... <= T where P is the result you have to prove and T what you already know .
I would let them know of course...
Original post by jjsnyder
Only reason I can think of that I would ask for spare unmarked paper is when I am proving a condition one way, but I want to start in reverse, so I do the reverse calculations on a rough sheet then put them the right way on the actual answer booklet (and that way the examiner doesn't think bad of you). Can we do this in the exam?


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I was thinking of using the back page or something for rough work if they don't give me rough paper. I always need to do rough work/trial things on a separate sheet of paper otherwise it would completely interfere with my solution.
Original post by Vesniep
I do that many times ( idk if it's wrong)

P <= Q <= R ... <= T where P is the result you have to prove and T what you already know .
I would let them know of course...


Yeah I usually write "P⇔Q⇔R⇔...⇔TP \Leftrightarrow Q \Leftrightarrow R \Leftrightarrow ... \Leftrightarrow T, which is true, so result follows."
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Original post by jjsnyder
Only reason I can think of that I would ask for spare unmarked paper is when I am proving a condition one way, but I want to start in reverse, so I do the reverse calculations on a rough sheet then put them the right way on the actual answer booklet (and that way the examiner doesn't think bad of you). Can we do this in the exam?


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Original post by IrrationalRoot
I was thinking of using the back page or something for rough work if they don't give me rough paper. I always need to do rough work/trial things on a separate sheet of paper otherwise it would completely interfere with my solution.


You can ask for and will be given rough paper, it's just that even your scratch workings that look really untidy might give you a mark or two that you might miss out on whilst writing the neat version up (even if it's scratched out!). Whereas there's literally no downside to writing the rough work in the booklet in terms of gaining marks.
Original post by Zacken
You can ask for and will be given rough paper, it's just that even your scratch workings that look really untidy might give you a mark or two that you might miss out on whilst writing the neat version up (even if it's scratched out!). Whereas there's literally no downside to writing the rough work in the booklet in terms of gaining marks.


The main reasons I need to do rough work on a separate sheet are that
1. I need my work to be as neat as possible to be able to follow what I'm doing well and make less silly mistakes (because that is a massive problem I have).
2. I need to trial different methods quite a lot, which would not work nearly as well if I had to put these in my solution since I'd be using loads of paper and most of my work would be messy scribbling (so basically 1.)

I wouldn't mind doing all rough work in the booklet too much but it would have to be on a separate page and I'm not sure it would earn any marks there.
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Original post by Geraer100
Just to make sure, when drawing a graph, are there some features that must be find like asymptotes, stationary points, points that cross x, y axis , symmetry or it really depends on the question? And sketch and draw I guess they are the same no? Sorry if the question is a bit silly.:smile:


I think you should always justify the features of your sketch unless it's obvious that the question wants very little detail or it's very hard to determine the features and you can't see the question asking that. So for the most part, always justify and sketch/label features like asymptotes/stationary values/intercept-values.

Original post by Themathgeek
Sorry I just realised how unclear that was

How do you know that the horizontal velocity is 0 when T= Ucostheta/(kg) ?

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Can you see that x˙=ucos⁡θ−kgt\dot{x} = u\cos \theta - kgt? (that stems from integrating x¨=−kg\ddot{x} = -kg and plugging in the relevant boundary conditions), if so - set x˙=0⇒ucos⁡θ=kgt⇒⋯\dot{x} = 0 \Rightarrow u\cos \theta = kgt \Rightarrow \cdots
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Original post by IrrationalRoot
The main reasons I need to do rough work on a separate sheet are that
1. I need my work to be as neat as possible to be able to follow what I'm doing well and make less silly mistakes (because that is a massive problem I have).
2. I need to trial different methods quite a lot, which would not work nearly as well if I had to put these in my solution since I'd be using loads of paper and most of my work would be messy scribbling (so basically 1.)

I wouldn't mind doing all rough work in the booklet too much but it would have to be on a separate page and I'm not sure it would earn any marks there.


Hmm, yeah, I do suppose in that case since it helps you focus on your work more, that it might be best to do some working on rough paper. Your centre will definitely provide that for you. :yep:
Do we have the time before the II exam to improve in geometry and vector questions significantly? It seems like flooding the pure with those types of questions would be an easy miss of an offer for me, unless there are also good mech questions.


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Original post by Insight314
Do we have the time before the II exam to improve in geometry and vector questions significantly? It seems like flooding the pure with those types of questions would be an easy miss of an offer for me, unless there are also good mech questions.


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Not much time, can if you like but the good news is that if lots of vectors/geometry comes up they know people like those questions less and grade boundaries would be accordingly low.


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Original post by IrrationalRoot
Yeah I usually write "P⇔Q⇔R⇔...⇔TP \Leftrightarrow Q \Leftrightarrow R \Leftrightarrow ... \Leftrightarrow T, which is true, so result follows."


What if you can't use <=> and the left statements are less general .
That's when I use <= .
Actually I want to ask is it wrong to claim P=>Q when P,Q are equivalent ?
It's kind of tricky because P implies Q so it's true but these symbols refer to what P and Q are to each other and since they are equivalent P=>Q is wrong . Idk if that makes sense, just answer.
Original post by Zacken
I think you should always justify the features of your sketch unless it's obvious that the question wants very little detail or it's very hard to determine the features and you can't see the question asking that. So for the most part, always justify and sketch/label features like asymptotes/stationary values/intercept-values.
/QUOTE]

Okay, thanks for that. And my plan for the STEP is to spend 5/10 minutes looking and deciding the order of the questions that I am going to do. So I will start with the easy ones and then when I get stuck, I will spend 5/10 minutes to try to solve the problem but if I cannot really solve it, then I will move on. And if there is not a lot of time left at the end and I still haven't attempted 6 questions. I wonder if it's better to start new question and gain the first few easy marks or go back to try to complete more full solutions. (This is problem that I usually encountered when doing mocks, I took too much time thinking which choice is better).

Do you think the plan is fine?
(edited 7 years ago)

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