• Congratulations to the Class of 2024 on your results!
    Let us know how you went here
    Got a question about your uni preferences? Ask us here

some1 noe answer for the last question (1 Viewer)

jarro_2783

Member
Joined
Dec 1, 2004
Messages
63
Location
Australia
Gender
Male
HSC
2005
yes that is correct. Was that the one with the protons. You were meant to use the two force equations to end up with mv = qBr or something like that.
 

ying123123

Member
Joined
Oct 20, 2005
Messages
43
okay this is wat i got
dont think if its right
centripetal force (the result had and radius so yeah)
and f=qvb
mv=p
then p=qrB
 

Captain Gh3y

Rhinorhondothackasaurus
Joined
Aug 10, 2005
Messages
4,153
Location
falling from grace with god
Gender
Male
HSC
2005
Ok, here's how it worked:

(i) The particle is in a magnetic field, and also has centripetal force (the hint was 'circular path with radius...')

so F = qvB = mv²/r

Rearranging that, you get mv = qBr.


(ii) All of the values for the above were given, except for q, which is 1.602x1019C (from data sheet), so simple substitution to get the mass of a proton, as observed by someone standing outside the accelerator and watching it move.

(iii) Apply the mass dilation formula in reverse, ie.
mv = mo/√(1-v²/c²)
mv is what you found in part (ii), so rearranging
mo = mv*√(1-v²/c²)

Then you substituted in the velocity and your answer to part (ii), and got a mass, a bit smaller than the value in part (ii).
 

Haku

Member
Joined
Nov 12, 2004
Messages
779
i ran out of time and didn't get any of that. couldn't think when i am short on time....
 

thunderdax

I AM JESUS LOL!
Joined
Jan 28, 2005
Messages
278
Location
Newcastle
Gender
Male
HSC
2005
The answer for (iii) should have matched with the data sheet to 3 significant figures.
 

thunderdax

I AM JESUS LOL!
Joined
Jan 28, 2005
Messages
278
Location
Newcastle
Gender
Male
HSC
2005
yeah, it was 1.67e-27 which is the same as the data sheet to 3 significant figs.
 

richz

Active Member
Joined
Sep 11, 2004
Messages
1,348
Captain Gh3y said:
Really?

My final answer for (iii) was similar to seadonkey's, somewhere near 1.66e-27... can't remember exactly.
yeah, it was eql to 1.666e-27 so 3SF = 1.67e-27
 

jake2.0

. . .
Joined
Sep 17, 2005
Messages
616
Gender
Male
HSC
2005
how come no one here took into account the weight force on the proton???

mind you i ended up getting the same answer
 
Joined
Sep 3, 2005
Messages
68
Location
Aus
Gender
Female
HSC
2005
woot! i got it!! gee it reli made me dive into equations and think to integrate these stuff together...:D
 

samaccount123

Member
Joined
Aug 20, 2008
Messages
119
Gender
Male
HSC
2006
Particle accelerators aren't THAT small..I didn't understand this qstn much to get it I think..
 

samaccount123

Member
Joined
Aug 20, 2008
Messages
119
Gender
Male
HSC
2006
Particle accelerators aren't THAT small..I didn't understand this qstn much to get it I think..
Oh yeah, darn..its travelled in a bubble chamber even though the cyclotron or something is as big as it is and the hydrogen deflects the proton/s..ugh
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top