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Help with integration/newton's law question (CCEA M2)?

Hey! :smile:

They've started putting the CCEA papers up for 2016. This is an M2 paper for use in either Further Maths or Maths, depending on your module combo. I know its a week before results, but I'm busting to know if I got this right:
vkmv.jpg

I can't remember my exact method, but it involved F=ma and integration. I ended up with t = 1/k ln(2) as far as I remember for part ii.

Can someone put me out of my misery before I crack? xD
(edited 7 years ago)
Original post by TiernanW
Hey! :smile:

They've started putting the CCEA papers up for 2016. This is an M2 paper for use in either Further Maths or Maths, depending on your module combo. I know its a week before results, but I'm busting to know if I got this right:

I can't remember my exact method, but it involved F=ma and integration. I ended up with t = 1/k ln(2) as far as I remember for part ii.

Can someone put me out of my misery before I crack? xD


a=dvdta=\frac{dv}{dt} which makes it a differential equation to be solved via integration.
Reply 2
Original post by RDKGames
a=dvdta=\frac{dv}{dt} which makes it a differential equation to be solved via integration.


I've gotten rusty over the summer.

So, mg - kmv = ma, so then gkv=dvdtg - kv = \frac{dv}{dt} and then do I put V/2 into v?
Original post by TiernanW
I've gotten rusty over the summer.

So, mg - kmv = ma, so then gkv=dvdtg - kv = \frac{dv}{dt} and then do I put V/2 into v?


No. You put in V2=g2k\frac{V}{2}=\frac{g}{2k} I believe, because you can work out k from the conditions given (t=0, v=0).then proceed to solve for t.
Reply 4
Original post by RDKGames
No. You put in V2=g2k\frac{V}{2}=\frac{g}{2k} I believe, because you can work out k from the conditions given (t=0, v=0).then proceed to solve for t.


Sorry to be distracting on this evening. I'm just desperate to know what to expect for this on results day because its driving me up the wall with anxiety. Even if I got this wrong I'd rather know now.

It wants the answer in terms of kk though, so would that not indicate that you can't work it out?

Are you saying I should sub g2k\frac{g}{2k} into as the v part of gkv=dvdtg-kv = \frac{dv}{dt}?
(edited 7 years ago)
Original post by TiernanW
Sorry to be distracting on this evening. I'm just desperate to know what to expect for this on results day because its driving me up the wall with anxiety. Even if I got this wrong I'd rather know now.

It wants the answer in terms of kk though, so would that not indicate that you can't work it out?


find v as a function of time
Original post by TiernanW
Sorry to be distracting on this evening. I'm just desperate to know what to expect for this on results day because its driving me up the wall with anxiety. Even if I got this wrong I'd rather know now.

It wants the answer in terms of kk though, so would that not indicate that you can't work it out?


Apologies, the evening is getting the better of me. What I meant was that when you integrate, you can work out the constant rather than k and plug in when I've mentioned before. The k's inside the ln cancel out but the one left outside doesn't. I've gotten the same answer you've mentioned in OP.
Reply 7
Original post by samb1234
find v as a function of time


SUVAT? Sorry I'm so rusty right now.
Original post by samb1234
find v as a function of time


No need.
Original post by TiernanW
SUVAT? Sorry I'm so rusty right now.


solve the de. Easiest way is to integrate between 0 and g/2k wrt v, and 0 and t wrt t
Reply 10
Original post by RDKGames
Apologies, the evening is getting the better of me. What I meant was that when you integrate, you can work out the constant rather than k and plug in when I've mentioned before. The k's inside the ln cancel out but the one left outside doesn't. I've gotten the same answer you've mentioned in OP.


Thank you so much for your help! :smile:

You have no idea how much this has taken off my shoulders; you've sent someone away very happy! :wink:
Original post by RDKGames
No need.


yeah true didn't read it properly no need to rearrange the solved de
Original post by TiernanW
Thank you so much for your help! :smile:

You have no idea how much this has taken off my shoulders; you've sent someone away very happy! :wink:

Glad to hear :tongue:

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