Edexcel M3 16 June 2011 SOLUTIONS IN FIRST POST

Here are the solutions.

I'm not actually an expert in this module so I can't really give any insight as to whether this was a hard paper or not or guess as to the grade boundaries.

Thanks to various people who have spotted some mistakes.
I'll update the solutions later but here they are:

3) CoM here was 8/9l from O. Which means the angle is 36.1. If you look I've done 45+36=111 Doh!

6) I need to sub the speed into the equation for tension to show T>0 as it passes through B. If you work it out T=6mg

EDIT: SOLUTIONS BELOW ARE NOW CORRECT

(edited 12 years ago)

M3 June 11 Model Solutions.pdf281.1KB

Reply 1

20100

Original post by Gibbo81

I've done the model solutions for this exam after a number of people requested that I do so.

I've made one mistake in q5 and the solution for b) should be root(gl)/2 and for c) should be 3l/4

I'll update the attachment when I get chance.

I'm losing about 18 marks with harsh marking... thats 57 raw... what did you think of the difficulty? It was harder than January

Any ideas on how much UMS would 57 raw be? Thank you for uploading, very helpful

(edited 12 years ago)

Reply 2

dgb93

36p(pi)l^3+45p(pi)l^3=81p(pi)l^3 (not 111) so on q3 i think the distance is 8l/9 and then 36.1 degrees for 3b) is this right??

Reply 3

sumo_sam8

Yeah I agree with dgb93
it should be 81
and then the left hand side goes to 72

Reply 4

wishwash

im not sure if its right, but isnt the condition for it to reach b for t>0?

Reply 5

lpmad

The com question with the hemisphere and cylinder should be 8/9l I agree with everythig else though!

Reply 6

dgb93

Original post by wishwash

im not sure if its right, but isnt the condition for it to reach b for t>0?

I think so, a rod just hasd to have v>0 but a string needs to have tension in the string also i found the tension to be 6mg i think and then said therefore t>0

Reply 7

snowflakesblues

1

I think I lost a gazillion marks. I got q(2) wrong from the start because of the formula :|

Reply 8

TwilightKnight

11

Original post by Gibbo81

Here are the solutions.

I'm not actually an expert in this module so I can't really give any insight as to whether this was a hard paper or not or guess as to the grade boundaries.

There seem to be a few mistakes on here (I'm not infallible - I know I've made mistakes on this paper as well) but:

3) You've found the CoM of a composite that you've double valued on without (seemingly) taking into account the double density. The general consensus is that the CoM here was 8/9l from O. Which means the angle is possibly wrong too. (Ft marks?).

5) You already said you spotted your mistake here.

6) You haven't actually proved that P with pass through B - what you've proved is the minimum speed that it will pass through B at - you needed to prove that T>0, which did include finding the speed in order to sub it into a tension equation.

Everything else looks ok.

Reply 9

TwilightKnight

11

Original post by 20100

I'm losing about 18 marks with harsh marking... thats 57 raw... what did you think of the difficulty? It was harder than January

Any ideas on how much UMS would 57 raw be? Thank you for uploading, very helpful

I would think it likely that the grade boundary for this paper for an A will be between 63 and 65, which would mean 57 would be roughly 70-74 UMS, i.e a B.

But don't mark yourself too harshly, you'd be surprised how many method marks you get in M3+.

Reply 10

Lucy23

Original post by 20100

I'm losing about 18 marks with harsh marking... thats 57 raw... what did you think of the difficulty? It was harder than January

Any ideas on how much UMS would 57 raw be? Thank you for uploading, very helpful

...............................................A*.A...B...C...D...E
Jan 2011 grade boundaries : 69 53 56 50 44 38
Jun 2010 grade boundaries : 69 53 56 50 44 38
Jan 2010 grade boundaries : .... 57 51 45 40 35
Jun 2009 grade boundaries : .... 48 42 46 30 25
Jan 2009 grade boundaries : .... 63 56 49 42 35

obviously there are no a* grade boundaries before last year

Reply 11

fudokung

mediafire link please

Reply 12

20100

It was deffo harder than January 2011 but not as hard as January 2010

I'm thinking

UMS: 100 90 80 70 60 50 40
RAW: 72 65 58 51 44 38 32

Reply 13

lpmad

Yea the angle should have been less! And did anyone else prove t was = 6mg? For 6?

Reply 14

sulexk

11

Thank you for your answers! :smile:

For the centre of mass question: I remember taking the centre of mass of the hemisphere as negative, perhaps that is why our answers differ?

Reply 15

sumo_sam8

What do people thing the grade boundaries will be for 100/90/80 ums?
I found the paper quite hard, but ive seen most people say they found it easy...

Whoops just realised people have already said..

(edited 12 years ago)

Reply 16

snowflakesblues

1

Will the examiner be really harsh when he sees that i got the bottom bit of the formula wrong for q(2) It should've been y^2 i put yx instead for some reason.............. V_V

Reply 17

wishwash

Original post by sumo_sam8

What do people thing the grade boundaries will be for 100/90/80 ums?
I found the paper quite hard, but ive seen most people say they found it easy...

Whoops just realised people have already said..

well, i honestly found it easy because most of it was to rove smth so i;d know if my answers were wrong, and most of the time, actually all the time, i lose marks on accuracy. but thats just me.
tho generally it was difficult for some and easy for some. no one really said inbetween :/ so maybe that might even out the grade boundaries!

Reply 18

ArchimedesSpiral

1

Original post by TwilightKnight

There seem to be a few mistakes on here (I'm not infallible - I know I've made mistakes on this paper as well) but:

3) You've found the CoM of a composite that you've double valued on without (seemingly) taking into account the double density. The general consensus is that the CoM here was 8/9l from O. Which means the angle is possibly wrong too. (Ft marks?).

Yes, I found 8/9l from O too.

6) You haven't actually proved that P with pass through B - what you've proved is the minimum speed that it will pass through B at - you needed to prove that T>0, which did include finding the speed in order to sub it into a tension equation.

Yes. The value I found for T was 6mg; would be interested to hear other peoples.

Reply 19

username549369

On question 6a, I managed to prove that T>0 at the top, but I think I got the wrong actual value of T. I'm hoping that won't cost me too many marks. I'm slightly unsure about that question as a whole. The rest of it looks ok. Though I can remember hardly any of my answers, some of them look familiar.

Edexcel M3 16 June 2011 SOLUTIONS IN FIRST POST

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