# FM1 question

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Hii please could someone help me with part b

thank youu

thank youu

Last edited by Qxi.xli; 1 month ago

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I'm just getting confused because e<0<=1 and we're told that 0<lambda<1/2, and I don't know which one I'm supposed to use, if that makes sense?

Last edited by Qxi.xli; 1 month ago

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#3

(Original post by

I'm just getting confused because e<0<=1 and we're told that 0<lambda<1/2, and I don't know which one I'm supposed to use, if that makes sense?

**Qxi.xli**)I'm just getting confused because e<0<=1 and we're told that 0<lambda<1/2, and I don't know which one I'm supposed to use, if that makes sense?

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(Original post by

can you post what you've tried?

**Muttley79**)can you post what you've tried?

how would I start it?

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#5

(Original post by

I mean I've tried equating the answer from part a, but it just turned into a mess and I wasn't getting anywhere near the answer.

how would I start it?

**Qxi.xli**)I mean I've tried equating the answer from part a, but it just turned into a mess and I wasn't getting anywhere near the answer.

how would I start it?

I got (a) from these. then use the restrictions ...

Last edited by Muttley79; 1 month ago

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(Original post by

Just do conservation of momentum equation and e x approach speed = separation speed

I got (a) from these.

**Muttley79**)Just do conservation of momentum equation and e x approach speed = separation speed

I got (a) from these.

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#7

(Original post by

oh I've got the answer to part a, I'm stuck on b?

**Qxi.xli**)oh I've got the answer to part a, I'm stuck on b?

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(Original post by

I edited my post - I rearranged the expression for e to get k.

**Muttley79**)I edited my post - I rearranged the expression for e to get k.

there are two? e<0<=1 and 0<lambda<1/2? Do I need to use both? If so which one should I start with?

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#9

(Original post by

which restrictions do I use?

there are two? e<0<=1 and 0<lambda<1/2? Do I need to use both? If so which one should I start with?

**Qxi.xli**)which restrictions do I use?

there are two? e<0<=1 and 0<lambda<1/2? Do I need to use both? If so which one should I start with?

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#10

**Qxi.xli**)

which restrictions do I use?

there are two? e<0<=1 and 0<lambda<1/2? Do I need to use both? If so which one should I start with?

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(Original post by

Well you want to find the minimum value of k, if that helps?

**laurawatt**)Well you want to find the minimum value of k, if that helps?

i mean λ<1/2 is the smallest?

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(Original post by

I used e as I said and got an inequality for k - it might not be the only approach

**Muttley79**)I used e as I said and got an inequality for k - it might not be the only approach

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#13

(Original post by

ok thanks, but if you had used the other inequality and got the correct answer, would you still get all the marks? x

**Qxi.xli**)ok thanks, but if you had used the other inequality and got the correct answer, would you still get all the marks? x

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**Qxi.xli**)

which restrictions do I use?

there are two? e<0<=1 and 0<lambda<1/2? Do I need to use both? If so which one should I start with?

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#15

(Original post by

mqb2766 ^ sorry for tagging you, please could you help😭 I just keep getting questions like these wrong ):

**Qxi.xli**)mqb2766 ^ sorry for tagging you, please could you help😭 I just keep getting questions like these wrong ):

e < 1

In terms of k?

Note, your original e < 0 < 1 isn't right as I'm sure you realize, it should be 0 < e < 1. The 0 < e is trivially satisfied (the numerator & denominator is positive) so just consider e < 1.

Last edited by mqb2766; 1 month ago

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(Original post by

What do you get when you rearrange the inequality

e < 1

In terms of k?

Note, your original e < 0 < 1 isn't right as I'm sure you realize, it should be 0 < e < 1. The 0 < e is trivially satisfied (the numerator & denominator is positive) so just consider e < 1.

**mqb2766**)What do you get when you rearrange the inequality

e < 1

In terms of k?

Note, your original e < 0 < 1 isn't right as I'm sure you realize, it should be 0 < e < 1. The 0 < e is trivially satisfied (the numerator & denominator is positive) so just consider e < 1.

oh yeah sorry, that was a typo.

so in questions like this, we always ignore the 0<e?

because if I had re-arranged e>0, it gives that gives kλ>-1. Isn't that important information? idk

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#17

(Original post by

that gives 1<k(-2λ +1)

oh yeah sorry, that was a typo.

so in questions like this, we always ignore the 0<e?

because if I had re-arranged e>0, it gives that gives kλ>-1. Isn't that important information? idk

**Qxi.xli**)that gives 1<k(-2λ +1)

oh yeah sorry, that was a typo.

so in questions like this, we always ignore the 0<e?

because if I had re-arranged e>0, it gives that gives kλ>-1. Isn't that important information? idk

k*lambda > 0 > -1

So trivially satisfied, so not important for this question.

Note that when lambda=0, e=1 and k=1, this was essentially a Newton's cradle question where a moving ball collides with a stationary, identical ball and the first ball is brought to a complete halt and transfers all its velocity to the second ball. This is the scenario that gives the k=1 condition.

Last edited by mqb2766; 1 month ago

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(Original post by

Thats (both) correct. For e > 0,

k*lambda > 0 > -1

So trivially satisfied, so not important for this question.

Note that when lambda=0, e=1 and k=1, this was essentially a Newton's cradle question where a moving ball collides with a stationary, identical ball and the first ball is brought to a complete halt and transfers all its velocity to the second ball. This is the scenario that gives the k=1 condition.

**mqb2766**)Thats (both) correct. For e > 0,

**, so**__k and lambda are both > 0__k*lambda > 0 > -1

So trivially satisfied, so not important for this question.

Note that when lambda=0, e=1 and k=1, this was essentially a Newton's cradle question where a moving ball collides with a stationary, identical ball and the first ball is brought to a complete halt and transfers all its velocity to the second ball. This is the scenario that gives the k=1 condition.

ohh wow nice that's cool

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(Original post by

Thats (both) correct. For e > 0, k and lambda are both > 0, so

k*lambda > 0 > -1

So trivially satisfied, so not important for this question.

Note that when lambda=0, e=1 and k=1, this was essentially a Newton's cradle question where a moving ball collides with a stationary, identical ball and the first ball is brought to a complete halt and transfers all its velocity to the second ball. This is the scenario that gives the k=1 condition.

**mqb2766**)Thats (both) correct. For e > 0, k and lambda are both > 0, so

k*lambda > 0 > -1

So trivially satisfied, so not important for this question.

Note that when lambda=0, e=1 and k=1, this was essentially a Newton's cradle question where a moving ball collides with a stationary, identical ball and the first ball is brought to a complete halt and transfers all its velocity to the second ball. This is the scenario that gives the k=1 condition.

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#20

(Original post by

Also, what do I do after that bit? where do I use this 0<lambda<1/2 lol😭

**Qxi.xli**)Also, what do I do after that bit? where do I use this 0<lambda<1/2 lol😭

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