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Can anyone help me re-arrange the T.OF Mass spec equations?

KE = 1/2mv2

This rearranges to

V = √(2KE/m)

Since v = d/t then we can replace v in the previous equation with d/t and we get

d/t = √(2KE/m)

Then multiply both sides by t gives

d = √(2KE/m) t

What do I do here? The TOF equation is suposed to be t= d x √(m/2KE)
I'm not sure how the equation sudenly flipped and how D is multiplied by the square root?
I would assume it would be D/ √(2KE/m) = t but what do I know im stupid :c
Original post by AlwaysBroke.
d = √(2KE/m) t

What do I do here? The TOF equation is suposed to be t= d x √(m/2KE)
I'm not sure how the equation sudenly flipped and how D is multiplied by the square root?
I would assume it would be D/ √(2KE/m) = t but what do I know im stupid :c

Starting with d=2KEmt d = \sqrt{\frac{2KE}{m}} t

then making t the subject by dividing both sides by 2KEm\sqrt{\frac{2KE}{m}}

t=d2KEmt = \frac{d}{ \sqrt{\frac{2KE}{m}}}

You then just turn the fraction upside down and use multiply instead (since dividing by 1/2 is the same as multiplying by 2)
Original post by EierVonSatan
Starting with d=2KEmt d = \sqrt{\frac{2KE}{m}} t

then making t the subject by dividing both sides by 2KEm\sqrt{\frac{2KE}{m}}

t=d2KEmt = \frac{d}{ \sqrt{\frac{2KE}{m}}}

You then just turn the fraction upside down and use multiply instead (since dividing by 1/2 is the same as multiplying by 2)

Hiya, thanks for the help but im just confused with this last part.
- why do we turn the fraction upside down and what do we multiply with?

like I dont understand how. Surely t = \frac{d}{ \sqrt{\frac{2KE}{m}}} is the most simplified version? its this part im stuck on :c
Thanks for the help though
Original post by AlwaysBroke.
Hiya, thanks for the help but im just confused with this last part.
- why do we turn the fraction upside down and what do we multiply with?

like I dont understand how. Surely t = \frac{d}{ \sqrt{\frac{2KE}{m}}} is the most simplified version? its this part im stuck on :c
Thanks for the help though

Sorry, my latex is a bit rusty!

t=d2KEmt = \frac{d}{ \sqrt{\frac{2KE}{m}}} is equivalent to the one that's quoted. It just looks different due to some minor algebraic tweaking.

Specifically, it's been adapted so that it isn't in the ''fraction of a fraction'' type format. You can stick the numbers into both and get the same answer.

Instead of x1/2\frac{x}{1/2} (i.e. fraction of a fraction) they've just flipped the 'denominator fraction' so that the two goes onto the top line. So it becomes 2x1=2x\frac{2x}{1} = 2x

In the question then:

t=d2KEm=dm2KE[br][br]t = \frac{d}{ \sqrt{\frac{2KE}{m}}} = d\sqrt{\frac{m}{2KE}}[br] [br]
Original post by EierVonSatan
Sorry, my latex is a bit rusty!

t=d2KEmt = \frac{d}{ \sqrt{\frac{2KE}{m}}} is equivalent to the one that's quoted. It just looks different due to some minor algebraic tweaking.

Specifically, it's been adapted so that it isn't in the ''fraction of a fraction'' type format. You can stick the numbers into both and get the same answer.

Instead of x1/2\frac{x}{1/2} (i.e. fraction of a fraction) they've just flipped the 'denominator fraction' so that the two goes onto the top line. So it becomes 2x1=2x\frac{2x}{1} = 2x

In the question then:

t=d2KEm=dm2KE[br][br]t = \frac{d}{ \sqrt{\frac{2KE}{m}}} = d\sqrt{\frac{m}{2KE}}[br] [br]

Ah I see!
Just to confirm like with the example above (X/1/2) can be written as X/1 ÷ 1/2.
We can flip this around to form X/1 x 2/1 giving us 2X/1

However when doing this method with the above answer I get:
______
d/1 ÷ 2ke/m
______
which gives D/1 x m/2Ke
______
which gives me √Dm/2Ke
_____
Instead of D x 2ke/m

:c
Original post by AlwaysBroke.
Ah I see!
Just to confirm like with the example above (X/1/2) can be written as X/1 ÷ 1/2.
We can flip this around to form X/1 x 2/1 giving us 2X/1


Yep, exactly.

However when doing this method with the above answer I get:
______
d/1 ÷ 2ke/m
______
which gives D/1 x m/2Ke
______
which gives me √Dm/2Ke
_____
Instead of D x 2ke/m

:c


Formatting on TSR isn't great :tongue: But your mistake appears to be on the line second from bottom. It's wrong to pull the D into the square root, it should be multiplying outside of it:

D/1 x m/2Ke = D x m/2Ke not Dm/2Ke

edit: also why does that racoon in your pic have such a big bum :tongue:
(edited 3 years ago)
Original post by EierVonSatan
Yep, exactly.



Formatting on TSR isn't great :tongue: But your mistake appears to be on the line second from bottom. It's wrong to pull the D into the square root, it should be multiplying outside of it:

D/1 x m/2Ke = D x m/2Ke not Dm/2Ke

edit: also why does that racoon in your pic have such a big bum :tongue:

RIIIIGHT OMG! AHA that great feeling when everything pulls together is so brilliant. Thanks you so much!
I'm so so sorry arghh I haven't done maths since lower school you see and my brain has turned to mush after this long holiday. I was in my second year of A-levels and my exams got cancelled so I have been on holiday for like 3 months now and counting.

Yeah Sorry about the formatting Idk how you managed to pull it off in your replies :biggrin:

and as for the racoon :wink: It must have been a picture I pulled off from my faviroute cartoon tv show 'Regular Show' from the character Rigby. I haven't used TSR in a while so I must've done this when I was younger and never bother to change it. The title of my name still stands though!
Original post by AlwaysBroke.
RIIIIGHT OMG! AHA that great feeling when everything pulls together is so brilliant. Thanks you so much!
I'm so so sorry arghh I haven't done maths since lower school you see and my brain has turned to mush after this long holiday. I was in my second year of A-levels and my exams got cancelled so I have been on holiday for like 3 months now and counting.


Well least you're trying to brush up a bit now rather than after you get your results and realise that you want to sit the exams :yy:

Yeah Sorry about the formatting Idk how you managed to pull it off in your replies :biggrin:


It's not your fault, it's TSR itself, it's got quite bad compared to how it used to be. The article here tells you how to use latex, but it takes some practise :yep: But considering you don't do maths anymore, it's not worth learning it now :smile:

and as for the racoon :wink: It must have been a picture I pulled off from my faviroute cartoon tv show 'Regular Show' from the character Rigby. I haven't used TSR in a while so I must've done this when I was younger and never bother to change it. The title of my name still stands though!


:laugh: fair enough!
(edited 3 years ago)

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