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Multiple Choice (3 Viewers)

breesy

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12 - Well, plank was the first to correctly explain the relationship, even if he did not believe it, nor could back it up, his explanation was still correct.

9 - Ring R will still have currents induced in it, albeit not as strong as the completed copper ring, the currents do not have to travel around the ring in order to oppose the magnetic field. Think of the swinging fork (ie: slits) through a magnetic field, it will still slow down due to the induced current in each section of the the metal, also think of the laminated transformer not the same use of eddy currents, but they will still be induced in each independant layer of the core.
 

KFunk

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mrkotter said:
Use the right hand grip rule to find the direction of magnetic field. In B the currents and still travel so the answer is C
But around a wire it's circular so it doesn't travel in a single direction.
 

serge

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physics should scale well this year
there was hardly any arguement in the chem MC
 

cziLofty

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*hits self in head and sinks from the physics community*
i think sleep might help me. oh well HSC is over...
 

ying123123

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question 5 should be c
u take an values for the speed say 50ms-1
get the initial vertical speed.
then u let y=0 use the fomular and compare y=ut+.5AT sqaure
 

sweet_chick

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Ok heres what i put,
1 A
2 D
3 B
4 C (D looks more like a diagram for orbital decay, as the redcution in speed is large and instantaneous compared to slow gradual for orbital decay i chose C)
5 B (but i admit im wrong)
6 B ( cause of the whole perpendicular to magnetic field crap)
7 D (although might be A, im sick of right hand palm rule)
8 C (current is induced the instant the switched is closed)
9 B (eddy currents will still be set up they will just be smaller)
10 B
11 B
12 A
13 C
14 B
15 D
 

jarro_2783

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there is one problem with the textbook which you failed to notice. The question in the exam said "... relationship between the intensity of black body radiation...", your textbook said "... on the photoelectric effect...". Your textbook and the question are two different things, planck is the correct answer.

These are the answers, don't argue, they're right. I'll explain each one as well.

1. A
Acceleration is constant (gravity), so it's not B or D, only the y speed is 0 at the top so it is not C so it is A.

2. D
That's all it can be, can't really explain that one.

3. B
Again, that's all it can be, you just have to know that one. But if you look at formulas F = mv2/r and F = GMm/d2 the little ms cancel out which is the mass of the space craft and that's basically how it works.

4. D
This question is kind of wierd, but the question says it fires a forward facing rocket. A forward facing rocket can only slow it down and force it to come in. I did some calculations and it doesn't come down enough to hit the earth, so it has to be D.

5. C
People have already proved that one. Don't be retarded and talk about how golf clubs disprove it because golf clubs don't hit at a constant velocity and when you can hit it at exactly the same velocity and at complementary angles then come back and tell me what happened. Golf balls are also effected by spin on the ball, anyway, it's C.

6. B
Wierd question, the earth's magnetic field is basically uniform on earth so rotating a wire in it would do nothing as there is no change in flux linkage. But assuming it works, the length does matter because it means more flux linkage, so more change in linkage, the speed matters because it is changing quicker, and the direction matters because it only produces a current if it is perpendicular to the wire.

7. D
Right hand palm rule, not much more to explain.

8. A or C, it's a bad question. At the instant you closed the switch, there would be a spike in current, because there was a change in flux linkage. But because it is DC it would drop off and there would be no current. However, the question says "...when the switch is closed...". Do they mean the instant the switch is closed, or while the switch is closed? If it is the second part it is A, if it is the first part it is C. Bad question.

9. C
Eddie currents will slow down the ring in Q. P is plastic and R isn't connected so no currents. Therefore C.

10. B
That's just the way transformers work. The currents will be produced on the thin strips thus reducing them from if C was used. For C the currents would be around the big fat top bit and all the bits of metal, so it is B.

11. B
The cathode rays push the paddle wheel showing that they are particles with mass and speed and momentum.

12. A
As I said above, it's talking about black body radiation, he was the one that came up with the theory and the curve that fit experimental data. Einstein did photoelectric effect and said that all light is quantised. Planck said energy at the atomic level was quantised.

13. A
Boron produces an excess of holes. The electrons from the valence band will jump into the dopant level producing holes. My textbook Jacaranda HSC Science has that picture as a p type which somewhere else in the book says a group 3 atom is substituted in place of a group 4, ie. Boron or Gallium, boron for this question so A.

14. B
102.8 Mhz = 102 800 000. That times plancks constant = 6.812x10-26

15. D
Right hand palm rule again. Current moving along with magnetic field means electrons will move to top of rod and although holes don't "move" electrons going one way means holes going the other way. So it is D.
 
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MC was pretty hard, lotsa guessing.

And as for that projectile motion question, my reasoning was that 45 degrees is the prime angle for projectile motion. 50 is 5 above (duh) and 40 is 5 below so they would land, theoretically, in the same spot... maybe?
 

ying123123

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from the look of peoples answers i got 12/15 moslty like so iam happy
anywayz HSC is over

lets get drunk and burn the gay notes thats fuken look like a shit hole in my room
 

puteruser

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ok i just joined this thing today usually i read it and stuff but i have never felt the urge to write nething on here ....how ever some of the reasonin many of u have put in to 1 of the questions is totally pointless...u have all falled into the trap of what my teacher warned me of...u have answered the question u want to answer rather than the question that is asked! im talkin about qu 5! it says EXPECTS!!!! he did not kno about all the formulas that have been dicussed and argued! he naturally would have expected that if the angle was increased and range would be increased! hello!!! read the question!
 

seadonkey

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jarro_2783
i got same as u... onlythis is 9B n i know that 4 sure. its abt induction in lenz law. max induction in copper ring but the hole in R copper ring reduces the induction so only temp emf is generated, howeer for an instant there will b emf induced

8C
7A pretty sure im right... but still could be wrong. its a generator
6 --> B but only guess cos Q sed "very low reisitance" [btw B field is from earth which moves from south to north]
 

serge

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puteruser said:
it says EXPECTS!!!! he did not kno about all the formulas that have been dicussed and argued! he naturally would have expected that if the angle was increased and range would be increased! hello!!! read the question!
hahaha...

that's relative...
Was Napoleon an idiot?
or did he nearly conquer
all of Europe?
 

~Hyperion~

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puteruser said:
ok i just joined this thing today usually i read it and stuff but i have never felt the urge to write nething on here ....how ever some of the reasonin many of u have put in to 1 of the questions is totally pointless...u have all falled into the trap of what my teacher warned me of...u have answered the question u want to answer rather than the question that is asked! im talkin about qu 5! it says EXPECTS!!!! he did not kno about all the formulas that have been dicussed and argued! he naturally would have expected that if the angle was increased and range would be increased! hello!!! read the question!
then he be one retarded student i'm afraid
 

seadonkey

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range Q is C

think abt it from maths pov

R= V^2 sin 2theta/g

sine 80 = sine 100

also think abt it from physics pov
y velocity = Vsin theta
n y velocity determines time of flight
 

jarro_2783

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For nine the eddy currents are produced around the thing. But because the ring isn't complete there are no currents produced. So it is the same as plastic making R and P arrive at the same time making the answer Q.
I've seen it in a demonstration.
For 7 it's D because if you use the right hand palm rule you find that it is D. Here's how to work it out. Take one section of the loop, right side for example.
Now do the right hand palm thing and you will see that your thumb ends up pointing up the page which is the direction for D.
 
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seadonkey

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jarro_2783 said:
For nine the eddy currents are produced around the thing. But because the ring isn't complete there are no currents produced. So it is the same as plastic making R and P arrive at the same time making the answer Q.
I've seen it in a demonstration.
but still there will b induction only that is isnt continuous as in Q
think abt moving a rod in a B field at constant velocity. the rod will still slow down becuase of tempt induction but then cruise along at a slow speed then wen it entered the b field
 

serge

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jarro_2783 said:
But because the ring isn't complete there are no currents produced.
no, its just the size of the currents is smaller...

there are still eddy's induced, you can induce them in a sheet of metal?
so a bent sheet of metal (ring with a gap) will have them induced aswell
 

seadonkey

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serge said:
no, its just the size of the currents is smaller...

there are still eddy's induced, you can induce them in a sheet of metal?
so a bent sheet of metal (ring with a gap) will have them induced aswell
yep i know its just the size. bt just used this anaolgy 2 show wat i ment. lookin from both pov they will result in induction but not as much as Q
 

yaar_panjabi

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Question 5

question no. 5 is definetly C....because do calculations and u will get different times. 45 degrees gives max range.. so range from 50 degrees and 40 degrees will b same..cos complementry...USING v = u + at ..and say firing was done at 12 m/s for both shots... then if u do calculations using initial vertical velocity 12sin50 ..to find time..to max height then total time..using 12sin50 to calculate total time..is larger than using 12sin40..therefore it takes longer time definetly C...12 i s an example used.for both firings of same speed...
 

cziLofty

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ok i guess we will have to wait for real answers to put us at peace but for now i can say these answers are correct for SURE, id bet my life on it. or god help me im living in the wrong universe.
1A
9C
end of discussion for those questions (if your still unsure go back over this thread again)
 

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