Qxi.xli
Badges: 20
Rep:
?
#1
Report Thread starter 1 month ago
#1
Hii please could someone help me with part b Name:  Capture.PNG
Views: 11
Size:  233.1 KB
thank youu
Last edited by Qxi.xli; 1 month ago
0
reply
Qxi.xli
Badges: 20
Rep:
?
#2
Report Thread starter 1 month ago
#2
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
0
reply
Muttley79
Badges: 20
Rep:
?
#3
Report 1 month ago
#3
(Original post by 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?
can you post what you've tried?
0
reply
Qxi.xli
Badges: 20
Rep:
?
#4
Report Thread starter 1 month ago
#4
(Original post by Muttley79)
can you post what you've tried?
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?
0
reply
Muttley79
Badges: 20
Rep:
?
#5
Report 1 month ago
#5
(Original post by 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?
Just do conservation of momentum equation and e x approach speed = separation speed

I got (a) from these. then use the restrictions ...
Last edited by Muttley79; 1 month ago
0
reply
Qxi.xli
Badges: 20
Rep:
?
#6
Report Thread starter 1 month ago
#6
(Original post by Muttley79)
Just do conservation of momentum equation and e x approach speed = separation speed

I got (a) from these.
oh I've got the answer to part a, I'm stuck on b?
0
reply
Muttley79
Badges: 20
Rep:
?
#7
Report 1 month ago
#7
(Original post by Qxi.xli)
oh I've got the answer to part a, I'm stuck on b?
I edited my post - I rearranged the expression for e to get k.
0
reply
Qxi.xli
Badges: 20
Rep:
?
#8
Report Thread starter 1 month ago
#8
(Original post by Muttley79)
I edited my post - I rearranged the expression for e to get k.
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?
0
reply
laurawatt
Badges: 21
Rep:
?
#9
Report 1 month ago
#9
(Original post by 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?
Well you want to find the minimum value of k, if that helps?
0
reply
Muttley79
Badges: 20
Rep:
?
#10
Report 1 month ago
#10
(Original post by 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?
I used e as I said and got an inequality for k - it might not be the only approach
0
reply
Qxi.xli
Badges: 20
Rep:
?
#11
Report Thread starter 1 month ago
#11
(Original post by laurawatt)
Well you want to find the minimum value of k, if that helps?
no, still confused lol
i mean λ<1/2 is the smallest?
0
reply
Qxi.xli
Badges: 20
Rep:
?
#12
Report Thread starter 1 month ago
#12
(Original post by Muttley79)
I used e as I said and got an inequality for k - it might not be the only approach
ok thanks, but if you had used the other inequality and got the correct answer, would you still get all the marks? x
0
reply
Muttley79
Badges: 20
Rep:
?
#13
Report 1 month ago
#13
(Original post by 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
Getting an expression for e seems the logical approach as you've done that for (a) - I haven't tried getting an expression for lambda but it looks more tricky
0
reply
Qxi.xli
Badges: 20
Rep:
?
#14
Report Thread starter 1 month ago
#14
(Original post by 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?
mqb2766 ^ sorry for tagging you, please could you help😭 I just keep getting questions like these wrong ):
0
reply
mqb2766
Badges: 19
Rep:
?
#15
Report 1 month ago
#15
(Original post by Qxi.xli)
mqb2766 ^ sorry for tagging you, please could you help😭 I just keep getting questions like these wrong ):
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.
Last edited by mqb2766; 1 month ago
0
reply
Qxi.xli
Badges: 20
Rep:
?
#16
Report Thread starter 1 month ago
#16
(Original post by 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.
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
0
reply
mqb2766
Badges: 19
Rep:
?
#17
Report 1 month ago
#17
(Original post by 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
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.
Last edited by mqb2766; 1 month ago
0
reply
Qxi.xli
Badges: 20
Rep:
?
#18
Report Thread starter 1 month ago
#18
(Original post by 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.
hang on sorry where did you get this from?

ohh wow nice that's cool
0
reply
Qxi.xli
Badges: 20
Rep:
?
#19
Report Thread starter 1 month ago
#19
(Original post by 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.
Also, what do I do after that bit? where do I use this 0<lambda<1/2 lol😭
0
reply
Muttley79
Badges: 20
Rep:
?
#20
Report 1 month ago
#20
(Original post by Qxi.xli)
Also, what do I do after that bit? where do I use this 0<lambda<1/2 lol😭
What did you get as your inequality for k? Then you use the lambda part .... post your working.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

How would you feel if uni students needed to be double vaccinated to start in Autumn?

I'd feel reassured about my own health (33)
15.21%
I'd feel reassured my learning may be less disrupted by isolations/lockdowns (66)
30.41%
I'd feel less anxious about being around large groups (25)
11.52%
I don't mind if others are vaccinated or not (18)
8.29%
I'm concerned it may disadvantage some students (12)
5.53%
I think it's an unfair expectation (60)
27.65%
Something else (tell us in the thread) (3)
1.38%

Watched Threads

View All