M3 Edexcel June 16th Revision Thread

The normal reaction is normal (perpendicular) to the surface on which the particle is resting (or moving), so if it is on a sphere, the normal reaction points away from the centre of the sphere.

If the particle is inside a hemispherical bowl, however, the reaction force will point towards the centre of the sphere.

thanks for your help! but how do I know whether the particle is inside or outside? The questions never specify this...

Reply 21

ArchimedesSpiral

1

I've been working through past papers. Some of the old exam papers have oddly phrased questions, but up to now I've been able to understand everything. But there's one question from the June 2004 paper that I can't make any headway on.

I managed to get the right answer for (a) by using energy considerations, although I found the PE energy calculation kind of tricky (if you lot can't figure it out, I can upload my working for that question.) But I'm stumped as for the rest.

For (b), I assumed that the normal reaction at C would simply be mg -- since the tangent to C is horizontal. This doesn't seem to be right, although the markscheme writes R = mg, they seem to substitute a value of 890/50 for g? I don't even remotely understand the rest of the question.

This question seems unlike any other M3 question I've come across; but the spec for mechanics is supposed not to have changed since 2002! So I'm scared that a question like this is going to crop up on the exam.

Can anyone provide any insight into this question?

Thanks

Original post by ArchimedesSpiral

I've been working through past papers. Some of the old exam papers have oddly phrased questions, but up to now I've been able to understand everything. But there's one question from the June 2004 paper that I can't make any headway on.

I managed to get the right answer for (a) by using energy considerations, although I found the PE energy calculation kind of tricky (if you lot can't figure it out, I can upload my working for that question.) But I'm stumped as for the rest.

For (b), I assumed that the normal reaction at C would simply be mg -- since the tangent to C is horizontal. This doesn't seem to be right, although the markscheme writes R = mg, they seem to substitute a value of 890/50 for g? I don't even remotely understand the rest of the question.

This question seems unlike any other M3 question I've come across; but the spec for mechanics is supposed not to have changed since 2002! So I'm scared that a question like this is going to crop up on the exam.

Can anyone provide any insight into this question?

Thanks

From b to d it is a circular motion question therefore there is a centripetal force made up of the reaction minus the weight. 890/50 =mv^2/r

(edited 12 years ago)

Reply 23

philippat

has anyone done Jan 2004 question 7f? I can't figure out the angle, as I am finding 60 degrees, when its actually 73. Can someone please help me? :smile:

Reply 24

snowflakesblues

1

Can someone help me with part b) of the question? A light elastic string of natural length 0.5m is stretched between two points P and Q on a smooth horizontal table. The distance PQ is 0.75m and the tension in the string is 15N.
a) find the modulus of elasticity of the string. ...30N
b) A particle of mass 0.5kg is attached to the mid point of the string. The particle is pulled 0.1m towards Q and released from rest. Find the speed of the particle as it passes through the mid point of PQ.

I'm confused as to how to go about this... :s-smilie:

and almost all the other questions that get extended in the middle and pulled towards the other end? :s-smilie:

...if you could help provide some detailed explanations to, I would be very very grateful.

Reply 25

username549369

Maybe using conservation of energy?
So take the EPE when it is pulled towards Q, and the EPE at the mid-point, then subtract them to get the KE.
This seems like the most obvious thing to do, especially as they give you the mass of the particle in this part of the question so you can find the speed from the KE

Reply 26

Ammelia

11

One week till this paper and I'm STILL failing. Aaargh!
Chapters 3+4 are just slowly killing me, and we've not even finished chapter 5.

Reply 27

snowflakesblues

1

Original post by Supernovae

Maybe using conservation of energy?
So take the EPE when it is pulled towards Q, and the EPE at the mid-point, then subtract them to get the KE.
This seems like the most obvious thing to do, especially as they give you the mass of the particle in this part of the question so you can find the speed from the KE

Thanks, that what I thought

EPE loss = KE gain.

The bit im confused about is how to work out the EPE when it changes on both sides.

Sorry didn't explain it properly earlier.

Never mind I just got it thanks :smile:

(edited 12 years ago)

Reply 28

snowflakesblues

1

Original post by Ammelia

One week till this paper and I'm STILL failing. Aaargh!
Chapters 3+4 are just slowly killing me, and we've not even finished chapter 5.

I feel ur pain V_V This is the hardest A2 im taking... the rest of the modules seem fine V_V

Reply 29

username549369

Original post by snowflakesblues

Thanks, that what I thought

EPE loss = KE gain.

The bit im confused about is how to work out the EPE when it changes on both sides.

Sorry didn't explain it properly earlier.

The general EPE equation for both sides will have most values the same, you just need to work out the extensions for both sides. So first work out the EPE for the mid-point, as the extension is the same as when you worked out the modulus in part a. Then you have to work out the extension for the other bit, it's probably easier to draw a diagram.
Hope this helps

Reply 30

snowflakesblues

1

Original post by Supernovae

The general EPE equation for both sides will have most values the same, you just need to work out the extensions for both sides. So first work out the EPE for the mid-point, as the extension is the same as when you worked out the modulus in part a. Then you have to work out the extension for the other bit, it's probably easier to draw a diagram.
Hope this helps

Thank yewww :smile:

Reply 31

chaz1992

15

Need marking help guys.

The answer to a question in a past paper is lambda = 12.7, but I left my answer as 324mg/125 as I didn't realise the mass of the particle (0.5kg) was given. Would I lose any marks for this?

Reply 32

dullcia

Guys any help with question b)??? :smile:

please explain why, when(or if) you bother solving it please !!! :smile:

(edited 12 years ago)

Screen shot 2011-06-10 at 11.52.59 PM.png313.0KB

Reply 33

CapsLocke

OP

11

Original post by dullcia

Guys any help with question b)??? :smile:

please explain why, when(or if) you bother solving it please !!! :smile:

just treat it as if you're working out the centre of mass of the whole thing. you know where the centre of mass is, or if you don't look at the question again, then form an equation with L and solve it.

Reply 34

LethalResistant

How did everyone find the 2009 Jun past paper where the grade boundary for an A was like 64%?

Reply 35

BDS06

Can anyone help if they have the old M3 book. the one with the purple M on it

Its question 9 from ex4d,

Reply 36

username549369

Are the pre- 2007 past papers worth doing?

Reply 37

snowflakesblues

1

Any good tips guys :smile:

?

Reply 38

chaz1992

15

Considering the GB haven't been posted yet, here they are:

Session 100 90 80 70 60 50 40 (UMS)
Jun-01 66 59 52 45 38 31 25
Jan-02 73 66 59 52 45 38 31
Jun-02 75 68 61 53 46 39 32
Jan-03 72 66 60 54 48 43 38
Jun-03 70 63 56 49 42 35 28
Jan-04 65 59 53 47 41 36 31
Jun-04 70 63 56 49 43 37 31
Jan-05 67 60 53 46 40 34 28
Jun-05 68 61 54 47 40 33 27
Jan-06 72 65 58 51 44 38 32
Jun-06 68 61 54 47 41 35 29
Jan-07 70 63 56 49 42 35 29
Jun-07 75 70 65 57 49 42 35
Jan-08 69 62 55 48 41 34 27
Jun-08 71 64 57 50 43 37 31
Jan-09 75 69 63 56 49 42 35
Jun-09 60 54 48 42 36 30 25
Jan-10 69 63 57 51 45 40 35
Jun-10 75 69 63 56 50 44 38
Jan-11 75 69 63 56 50 44 38

June 2009 paper was a nightmare. Need 83UMS in this paper :s-smilie:

. Considering the June 2010 and Jan 2011 paper had a 100UMS cap at 75/75 (unusual for M3), could this coming paper be ridiculously hard? Hope not!