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AQA A2 MM2B Mechanics 2 – 27th June 2016 [Exam Discussion Thread]

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Does anyone have a set formula that works for EPE questions.

Like Final KE - Initial KE = Initial EPE - Final EPE - Work done by friction

Well the initial energy is going to be equal to the final energy, so you just need to ensure that you include KE, GPE, EPE and any other work (e.g. Friction or other resistive forces...)

Initial KE + Initial GPE + Initial EPE + Any other initial energy = Final KE + Final GPE + Final EPE + Any other energy used

Reply 61

TheKian

Original post by bartbarrow

Well the initial energy is going to be equal to the final energy, so you just need to ensure that you include KE, GPE, EPE and any other work (e.g. Friction or other resistive forces...)Initial KE + Initial GPE + Initial EPE + Any other initial energy = Final KE + Final GPE + Final EPE + Any other energy used

Are any of them ever negative and where to the resistive forces come in?

(edited 7 years ago)

Reply 62

JPencil

Anyone else looking forward to this exam? :biggrin:

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Reply 63

bartbarrow

Original post by TheKian

Are any of them ever negative and where to the resistive forces come in?

Remembering some formula won't help, you should just think in terms of "all of the energy in must be equal to all of the energy out"

The only time any of those are going to be negative is once you've rearranged them.

If you know there is a 4000N opposing force and it's moving 10m then W=Fd, so your work done by friction is 40,000J

So whenever you're doing a question like that, literally just sum all of the energy the particle has at the start and equate it to all of the energy it has at the end. There's nothing special to remember and the only time that will go wrong is if you forget to include a term.

(edited 7 years ago)

Reply 64

TheKian

Original post by JPencil

Anyone else looking forward to this exam? :biggrin:

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HELL NO, this is the final nail in the coffin

Reply 65

JPencil

Original post by TheKian

HELL NO, this is the final nail in the coffin

I think a good understand of M1 and A2 Physics has really helped. I've got two more exams after M2 :frown:

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Reply 66

2014_GCSE

What does "Resolve Radially" mean? I keep seeing it in the mark-schemes...

Reply 67

Hjyu1

Original post by 2014_GCSE

What does "Resolve Radially" mean? I keep seeing it in the mark-schemes...

Towards centre

Reply 68

Hjyu1

Original post by JPencil

Anyone else looking forward to this exam? :biggrin:

Posted from TSR Mobile

No cause this exam is the difference between a top rate education and working at the chippy down the road

Reply 69

Jm098

Original post by JPencil

I think a good understand of M1 and A2 Physics has really helped. I've got two more exams after M2 :frown:

Posted from TSR Mobile

Same

D2 and G485.. I think M2 is nice too. it's just going to be interesting to see what hard question they throw on there.

Reply 70

IrrationalRoot

Just did 2015 M2. That was... different, harder than 2014 for sure. I get the feeling they're trying to introduce more questions where there are no parts, just work out the method and everything else on your own, which is nice :smile:

. Last question was particularly harsh lol.
I'd like tomorrow's paper to be similar :biggrin:

Reply 71

JPencil

Original post by Jm098

Same

D2 and G485.. I think M2 is nice too. it's just going to be interesting to see what hard question they throw on there.

I hope Q8 (assuming we don't get 9) is an elastic one, I like those. I think D2 is going to be a killer, I still don't know some parts of the spec. What is G485? I have Phya4 (Physics)

Reply 72

JPencil

Original post by IrrationalRoot

. Last question was particularly harsh lol.
I'd like tomorrow's paper to be similar :biggrin:

What raw did you get on 2015? if you don't mind me asking. I'm about to do it as my offical mock, wish me luck :wink:

Reply 73

Jm098

Original post by JPencil

I hope Q8 (assuming we don't get 9) is an elastic one, I like those. I think D2 is going to be a killer, I still don't know some parts of the spec. What is G485? I have Phya4 (Physics)

Yeah me too, and not like last years haha... I wouldn't have been able to do it in the time! I think D2 is just not making mistakes really and G485 is the second module in OCR Physics :smile:

Reply 74

JPencil

Original post by Jm098

Yeah me too, and not like last years haha... I wouldn't have been able to do it in the time! I think D2 is just not making mistakes really and G485 is the second module in OCR Physics :smile:

I'm about to do 2015 as a mock. I'm actually looking forward to D2, from the bits I've done it seems nice. Do you know if we have to use simplex to find optimal mixed strategies?

Reply 75

IrrationalRoot

Original post by JPencil

What raw did you get on 2015? if you don't mind me asking. I'm about to do it as my offical mock, wish me luck :wink:

. Yep you'll do well provided you understand how all the methods work.

Reply 76

TheLifelessRobot

Original post by snimkar

Centripetal force causes the reaction to act inwards.

Does the reaction force always act towards the centre?

Reply 77

JC25

Original post by TheLifelessRobot

Does the reaction force always act towards the centre?

Depends on the context. Is it a bead on a wire? Ball on the inside of a tube? Ball on the outside of a hemisphere? Etc etc...

Reply 78

TheLifelessRobot

Original post by JC25

Depends on the context. Is it a bead on a wire? Ball on the inside of a tube? Ball on the outside of a hemisphere? Etc etc...

It was a bead on a wire, check page 3 for the question.

Reply 79

JC25

Whoops, sorry I missed that.

You don't actually know whether the reaction force acts inwards or outwards until you've done the question.

If you think about it, the velocity may be large enough for the reaction to be acting inwards but if the velocity is small enough the reaction may be outwards. Try and imagine a bead moving very quickly and then very slowly around the wire. Just model it one way and if you end up with a negative you know it's acting in the other direction to the way you modelled it and you can just ignore the minus sign.

Original post by TheLifelessRobot

It was a bead on a wire, check page 3 for the question.