[rainbowsss]

I hit a blank on the angular acceleration guy. What were u meant to do - Q6?

[tuckla07]

(Original post by XiaoXiao1)
That made this year's M4 look simple, that's impressive.

I know right! I was expecting a blood bath after the standard of the other exams edexcel have given me this year

[iluvmaths]

(Original post by rainbowsss)
I hit a blank on the angular acceleration guy. What were u meant to do - Q6?

-G=I(angular acceleration) then rearrange this to get the angular acceleration and use, w^2= (omega)^2+2(angular acceleration)(theta) and then because w was 0, just rearrange to find theta while subbing in the expression for angular acceleration in terms of G.

[Xtrapolation]

(Original post by rainbowsss)
I hit a blank on the angular acceleration guy. What were u meant to do - Q6?

Yeah that paper was stupid. The first 5 were pretty easy but I conked out on q6 (anyone remember what they got as the angular acceleration? I attempted that but left part (b)) and got the required result for the triangular lamina and hopelessly tried to fish out marks for the rest of it. Argh.

[iluvmaths]

(Original post by Xtrapolation)
Yeah that paper was stupid. The first 5 were pretty easy but I conked out on q6 (anyone remember what they got as the angular acceleration? I attempted that but left part (b)) and got the required result for the triangular lamina and hopelessly tried to fish out marks for the rest of it. Argh.

yeah, i think i got g/5r.

[kloitrell]

In Q6, I got g/7r for the angular acceleration before the string breaks. Then the pulley turns through an angle of Ω²mr²/G before it stops.

How about Q5? I got (67/60)mg for the force.

[rainbowsss]

(Original post by iluvmaths)
-G=I(angular acceleration) then rearrange this to get the angular acceleration and use, w^2= (omega)^2+2(angular acceleration)(theta) and then because w was 0, just rearrange to find theta while subbing in the expression for angular acceleration in terms of G.

Nah for part a, I wasnt sure how to consider a system with a particle on either side of the pulley...:/ can deal with one on one side but ..

I did T*r=I(angular accelration) for the pulley,but wasnt too sure how to consider the particles. mg-T=ma if there was only one ... ( giving you 2 simultaneous equtions to play with ofc)

[iluvmaths]

(Original post by kloitrell)
In Q6, I got g/7r for the angular acceleration before the string breaks. Then the pulley turns through an angle of Ω²mr²/G before it stops.

How about Q5? I got (67/60)mg for the force.

i agree with the Ω formula but not the angular acceleration. i got g/5r rather than 7r. could u explain ur working out?

[kloitrell]

(Original post by iluvmaths)
i agree with the Ω formula but not the angular acceleration. i got g/5r rather than 7r. could u explain ur working out?

See attachment for g/7r.
How did you get g/5r by the way?

It would be very nice if someone can upload the paper.

[iluvmaths]

(Original post by kloitrell)
See attachment for g/7r.
How did you get g/5r by the way?

It would be very nice if someone can upload the paper.

ohhh damn!!!! i thought the tensions in each string were the same!!!! ur right!

[rainbowsss]

(Original post by kloitrell)
See attachment for g/7r.
How did you get g/5r by the way?

It would be very nice if someone can upload the paper.

May I ask what revision materials you used? I used the edexcel M5 standard book which unfortunately didnt cover this, just curious ...

[XiaoXiao1]

(Original post by kloitrell)
In Q6, I got g/7r for the angular acceleration before the string breaks. Then the pulley turns through an angle of Ω²mr²/G before it stops.

How about Q5? I got (67/60)mg for the force.

Yeah I thought the tension would be different...after the exam.

I got 11/60 mg for 5; meh same denominator :P

[kloitrell]

(Original post by rainbowsss)
May I ask what revision materials you used? I used the edexcel M5 standard book which unfortunately didnt cover this, just curious ...

I used the edexcel book as well.

Actually that question is sort of a variant of Q7 of June 2006 paper (attached below). After that, just out of interest, I tried to find out the acceleration and the forces on the particles and found that the tensions are not the same.

By the way, Q6 in this exam is very similar to an example question in edexcel M1 textbook (also attached), with particles of the same masses but with the pulley being smooth and its moment of inertia ignored.

[pavlovscat]

(Original post by XiaoXiao1)
Yeah I thought the tension would be different...after the exam.

I got 11/60 mg for 5; meh same denominator :P

I got 11/60 mg as well, would be interested to hear what some others got? I wasn't sure of my answer at the time but hopefully even if it's not right there's some method marks up for grabs!

didn't need to do too well on this one, which was lucky since I didn't get the pulley question (assumed tensions the same and reached the answer far too quickly for an 8 marker so I at least knew it was wrong!) and didn't get the 7 marker proof by integration. What did people get for the radius of gyration? a/rt3 or something similar? (can't quite remember xD)

don't remember much else apart from my final v = ln(100/100-t) - 9.8t I think?

[Xtrapolation]

(Original post by pavlovscat)
I got 11/60 mg as well, would be interested to hear what some others got? I wasn't sure of my answer at the time but hopefully even if it's not right there's some method marks up for grabs!

didn't need to do too well on this one, which was lucky since I didn't get the pulley question (assumed tensions the same and reached the answer far too quickly for an 8 marker so I at least knew it was wrong!) and didn't get the 7 marker proof by integration. What did people get for the radius of gyration? a/rt3 or something similar? (can't quite remember xD)

don't remember much else apart from my final v = ln(100/100-t) - 9.8t I think?

Yes I got the same v(t) as you. I also got g/7r as the angular acceleration, but didn't attempt the braking force part.

[kloitrell]

I was wrong in Q5. (oh no!!!!) The answer is 11/60mg, not 67/60mg.
don't know why I got 67/60mg in the exam. My method was right so I should get some method marks.

I have also made the solution to Q2 and Q5, attached as pdf.

[rainbowsss]

(Original post by kloitrell)
I used the edexcel book as well.

Actually that question is sort of a variant of Q7 of June 2006 paper (attached below). After that, just out of interest, I tried to find out the acceleration and the forces on the particles and found that the tensions are not the same.

By the way, Q6 in this exam is very similar to an example question in edexcel M1 textbook (also attached), with particles of the same masses but with the pulley being smooth and its moment of inertia ignored.

ofc =]

[Xtrapolation]

(Original post by kloitrell)
I used the edexcel book as well.

Actually that question is sort of a variant of Q7 of June 2006 paper (attached below). After that, just out of interest, I tried to find out the acceleration and the forces on the particles and found that the tensions are not the same.

By the way, Q6 in this exam is very similar to an example question in edexcel M1 textbook (also attached), with particles of the same masses but with the pulley being smooth and its moment of inertia ignored.

You could of course have used L = I(dw/dt) which gave the same result of g/7r very quickly.

[kloitrell]

More solution!!

Unfortunately I can't remember Q1 (differential equation) and Q4 (system of forces, vector moment, etc.). I can't make a 'mark scheme' of those questions.

[MAD Phil]

Hi.

Just got back from a week's holiday in an isolated dale where you can't get a mobile signal, so I've only just seen the paper.

Here are my solutions.

Let me know about any mistakes.

Sorry I can't post the question-paper; the conditions for getting it from the Edexcel Emporium don't allow it.