• Best of luck to the class of 2024 for their HSC exams. You got this!
    Let us know your thoughts on the HSC exams here
  • YOU can help the next generation of students in the community!
    Share your trial papers and notes on our Notes & Resources page

General Thoughts: Physics (1 Viewer)

HecticLad

Member
Joined
Nov 29, 2014
Messages
78
Gender
Male
HSC
2015
does anybody know if my reasoning that the electric circuit wasn't closed (that 2 cm gap) means electrons cant be liberated from cathode and accel towards anode? i wrote that + electrons are - charge so its deflecting wrong way
what lol
 

Sarah Jane 1

New Member
Joined
Sep 30, 2014
Messages
21
Gender
Female
HSC
2016
What about the conductor that was circular and became rectangular (sorta) in the Multiple choice. Was the current anticlockwiseand the change in flux density? What about the forces on the parallel current carrying conductors? I think I got 3F/2 Newtons to the right
 

jackleung34

Member
Joined
May 7, 2014
Messages
74
Gender
Male
HSC
2015
holy shit that last space question RIP. Was the question looking for uses of "G" as in 6.67x10^-11 because i was talking about Forces of Universal gravitational attraction

What about the conductor that was circular and became rectangular (sorta) in the Multiple choice. Was the current anticlockwiseand the change in flux density? What about the forces on the parallel current carrying conductors? I think I got 3F/2 Newtons to the right
I'm fairly certain that q the answer was F/2 to the right
 

p0llex

Member
Joined
Jul 17, 2014
Messages
61
Gender
Male
HSC
2015
What about the conductor that was circular and became rectangular (sorta) in the Multiple choice. Was the current anticlockwiseand the change in flux density? What about the forces on the parallel current carrying conductors? I think I got 3F/2 Newtons to the right
Both wrong:

The flux density doesn't change when you change the shape, and Lenz's law says you create a magnetic field going in the same direction as the external one so it was clockwise.

P was attracting wire R while Q was pushing it away, but P was twice the distance, so it ended up as F/2 to the right.
 

HecticLad

Member
Joined
Nov 29, 2014
Messages
78
Gender
Male
HSC
2015
What about the conductor that was circular and became rectangular (sorta) in the Multiple choice. Was the current anticlockwiseand the change in flux density? What about the forces on the parallel current carrying conductors? I think I got 3F/2 Newtons to the right
nope the conductor one was clockwise with change in flux because it will induce a current to oppose the motion of the wire, and the flux density wasnt actually change because it was the same field

the parallel conductor one was F/2 to the right, because the middle conductor repelled it F to the right while the far conductor attracted it F/2 to the left, giving a vector sum of F/2
 

jackleung34

Member
Joined
May 7, 2014
Messages
74
Gender
Male
HSC
2015
Both wrong:

The flux density doesn't change when you change the shape, and Lenz's law says you create a magnetic field going in the same direction as the external one so it was clockwise.

P was attracting wire R while Q was pushing it away, but P was twice the distance, so it ended up as F/2 to the right.
aYYYyyyyYYYYYYYY lma0000000:headbang: :headbang: :headbang:
 

HecticLad

Member
Joined
Nov 29, 2014
Messages
78
Gender
Male
HSC
2015
holy shit that last space question RIP. Was the question looking for uses of "G" as in 6.67x10^-11 because i was talking about Forces of Universal gravitational attraction



I'm fairly certain that q the answer was F/2 to the right
question was talking about F=Gm1m2/r, which give equations such as escape velocity & orbital velocity
 

Crisium

Pew Pew
Joined
Feb 17, 2014
Messages
2,009
Location
Australia
Gender
Male
HSC
2015
question was talking about F=Gm1m2/r, which give equations such as escape velocity & orbital velocity
Yeah I talked about how Newton's Law of Universal Gravitation is used in the derivation of orbital velocity and the significance of this in regards to ensuring that the probe can maintain the orbit around Saturn
 

rhys-e

New Member
Joined
Jun 9, 2015
Messages
1
Gender
Male
HSC
N/A
It still applies for things which aren't projectiles, but in this case the electrons have some initial velocity which we don't know.

Best way of doing it I think was using qV=1/2mv^2, answer turned out to be somewhere between 7000 and 8000
What's qV? I equated work and kinetic energy (as work is equal to the change in kinetic energy). So Fs = 1/2mv^2 or qEs = 1/2mv^2. Answer came out to 4.1x10^7
 

malcolm21

Active Member
Joined
Nov 7, 2014
Messages
437
Gender
Male
HSC
N/A
question was talking about F=Gm1m2/r, which give equations such as escape velocity & orbital velocity
for this question did you have to equate these two? it wsa 3 marks and i did it in 1 line with v=root Gm/r
 

malcolm21

Active Member
Joined
Nov 7, 2014
Messages
437
Gender
Male
HSC
N/A
What's qV? I equated work and kinetic energy (as work is equal to the change in kinetic energy). So Fs = 1/2mv^2 or qEs = 1/2mv^2. Answer came out to 4.1x10^7
sick, i got this and i did the other formula, v^2 = u^2 + 2 (a) (s), im guessing we're right cause we used different formulas and still got the exact answer. Edit: I got 4.19 so ~ 4.2 actually
 

atargainz

Active Member
Joined
Jun 22, 2015
Messages
289
Gender
Male
HSC
2015
for this question did you have to equate these two? it wsa 3 marks and i did it in 1 line with v=root Gm/r
you would have to derive it, I did it by subbing T=2pir/v into keplers, gives v=root Gm/r
 

HecticLad

Member
Joined
Nov 29, 2014
Messages
78
Gender
Male
HSC
2015
for this question did you have to equate these two? it wsa 3 marks and i did it in 1 line with v=root Gm/r
that was a different question wasnt it, you wouldnt have to derive it
but for the 6 mark space one, it would have been good to explain that orbital & escape velocity are derived from the universal gravitation law
 

jackleung34

Member
Joined
May 7, 2014
Messages
74
Gender
Male
HSC
2015
i think the problem with this test was how vague some questions were in terms of what they were looking for. But I'd assume that's to seperate those who rote learned and those who do actually conceptually understand content

for this question did you have to equate these two? it wsa 3 marks and i did it in 1 line with v=root Gm/r
Referring to the last 6 marker of the test

What's qV? I equated work and kinetic energy (as work is equal to the change in kinetic energy). So Fs = 1/2mv^2 or qEs = 1/2mv^2. Answer came out to 4.1x10^7
Couldn't you have just found acceleration first through a=f/m, then used it to find final velocity upon hitting anode through v^2=u^2+2a(delta y)
 

p0llex

Member
Joined
Jul 17, 2014
Messages
61
Gender
Male
HSC
2015
What's qV? I equated work and kinetic energy (as work is equal to the change in kinetic energy). So Fs = 1/2mv^2 or qEs = 1/2mv^2. Answer came out to 4.1x10^7
Yep that's exactly what I did (qV is the same as qEs), but I got a different answer? Or maybe I'm thinking of the answer to a different question?

I'll have another go at it now
 

HecticLad

Member
Joined
Nov 29, 2014
Messages
78
Gender
Male
HSC
2015
i think the problem with this test was how vague some questions were in terms of what they were looking for. But I'd assume that's to seperate those who rote learned and those who do actually conceptually understand content
RIP those who didnt learn hertz's experiment
 

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

Top