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Edexcel Mechanics M4 and M5 13th and 19th June 2018 Exam Discussion

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I got a different answer for 5(c) mine had (ln(blah))^2 as in the natural log was squared

Do you mean it was the same thing, just with a "squared" at the end? Because that's what I wrote in the exam - just forgot to put it on here.

Reply 41

Redcoats

Any grade boundary estimates - I think it will be similar to 2012 boundaries

Reply 42

EdwardG

Original post by mupsman2312

Anyone else remember getting answers like these?

Q1: 8 Joules

Q2: a = -3.5 and b = 2.5

Q3: r = [cos^2(t/2) - 2cos^3(t/2)]i + [cos^2(t/2) + sin(t)]j

Q4: I = 16M/7

Q5(c): K.E. = (MU^2)/8[2 - ln(1 - lambda)] Joules

6(b): X = 3mg/2 and Y = sqrt(3)mg/2 ==> |F| = sqrt(3)mg

7(a): Period = 2pi.sqrt[(a^2 + 40l^2)/11gl] seconds
7(c): Impulse = 3m.sqrt[11g(a^2 + 40l^2)/2l] Ns

Some of the answers were so messy (particularly to Q7) - I *THINK* these are what I got.

I concur on 1, 2, 3, 4, 6. 5 I got a different answer, one I’m confident on. If you remember how you worked yours out we can have a look at that. Could you write your answers to 7 out on a piece of paper? Trying to decipher that mess is giving me a headache :smile:

. I’ll check that once you do.

Reply 43

mupsman2312

Original post by Redcoats

Any grade boundary estimates - I think it will be similar to 2012 boundaries

You're joking, right? It could be quite low, but THAT low? I'd love it if it is, but I can't see it myself. You never know, though - you could be right; it wasn't the nicest paper, in my opinion.

Reply 44

Redcoats

Original post by EdwardG

I concur on 1, 2, 3, 4, 6. 5 I got a different answer, one I’m confident on. If you remember how you worked yours out we can have a look at that. Could you write yours answers to 7 out on a piece of paper? Trying to decipher that mess is giving me a headache :smile:

. I’ll check that once you do.

I got that

Reply 45

Redcoats

Original post by mupsman2312

You're joking, right? It could be quite low, but THAT low? I'd love it if it is, but I can't see it myself. You never know, though - you could be right; it wasn't the nicest paper, in my opinion.

I was joking ... feebly

Maybe around 63-65.

What do you think?

Reply 46

mupsman2312

Original post by EdwardG

. I’ll check that once you do.

Actually, I'm pretty sure you're right on question 5 - I used the initial speed of the rocket as U instead of zero. Such a silly mistake! :angry:

If I did everything else right, could I still be looking at about 3-4/6?

I got all the way down to using SUVAT (v=u+at) with the correct values of t and a, but the wrong value of u (the only one that was actually given to you in the question!).

I'll write my answers to Q7 on paper, and put them in another post.

(edited 5 years ago)

Reply 47

Redcoats

Original post by EdwardG

. I’ll check that once you do.

I got something different for question 7

Reply 48

mupsman2312

Original post by Redcoats

I got a different answer for 5(c) mine had (ln(blah))^2 as in the natural log was squared

By the way, I've just realised that wasn't actually what I wrote in the exam, but I in fact put something else which was also wrong! I believe that what you said is correct - I've realised the silly mistake that I made on that question.

Reply 49

Redcoats

Original post by mupsman2312

That's ok. What do you think you've got out of 75?

Reply 50

mupsman2312

Here's a handwritten copy of my answers to 7(a) and 7(c):

M5 Exam Q7 001.jpg

Reply 51

mupsman2312

Original post by Redcoats

That's ok. What do you think you've got out of 75?

Depends upon question 7: if it's right, then potentially about 72; if not, then somewhere in the mid-to-high 60's most probably. What about you?

Reply 52

mupsman2312

Original post by Redcoats

I was joking ... feebly

Maybe around 63-65.

What do you think?

Probably high 60's for an A* (68-69). Could drop as low as 65, though. Here's hoping!

Reply 53

Redcoats

Original post by mupsman2312

Here's a handwritten copy of my answers to 7(a) and 7(c):

M5 Exam Q7 001.jpg

I accidently thought the rod was of length 2l so my answers are incorrect.

How many marks do you think I'll lose for that?

(edited 5 years ago)

Original post by Redcoats

I accidently thought the rod was of length 2l so my answers are incorrect.

How many marks do you think I'll lose for that?

I wouldn't like to say - I'm not the best at judging the leniency of the mark schemes.

If it's obvious that that's your only mistake, then you should hopefully still get all of the M marks and A ft marks.

Could you still show parts b and d? If so, then that's already 7 out of the 16 marks not to worry about.

Reply 56

Redcoats

Original post by mupsman2312

Depends upon question 7: if it's right, then potentially about 72; if not, then somewhere in the mid-to-high 60's most probably. What about you?

Maybe low to mid 60s

Reply 57

EdwardG

Original post by mupsman2312

Here's a handwritten copy of my answers to 7(a) and 7(c):

M5 Exam Q7 001.jpg

I’m am pleased to be able to confirm your answers, well, at least the last one. Can’t remember the others. Kept the 1/2 on the outside but aside from that identical.

Reply 58

mupsman2312

Did anyone else give their answer to the differential equation in either of these two forms?

r = [cos^2(t/2) - 2cos^3(t/2)]i + [cos^2(t/2) + 2sin(t/2)cos(t/2)]j

r = [cos^2(t/2) - 2cos^3(t/2)]i + [cos^2(t/2) + sin(t)]j

Reply 59

Redcoats

Original post by EdwardG

I’m am pleased to be able to confirm your answers, well, at least the last one. Can’t remember the others. Kept the 1/2 on the outside but aside from that identical.