Want to compare multiple-choice answers? (3 Viewers)

[nath_quam]

Can someone tell me what i got plz
1. C
2. B
3. D
4. B
5. C
6. A
7. C
8. A
9. B
10. A
11. A
12. C
13. D
14. C
15. A

i got 5/15 on my trial so hopefully better this time

 

[Nick_kirk]

hmm, ill post mine


1-C
2-B
3-D
4-B
5-D
6-A
7-C - I fell for the trap
8-A
9-Guess - B
10-D
11-A
12-C
13-D
14-C
15-A

 

[angmor]

The. Answer. For. Seven. Is. A.

AAA
A
A
A


Firstly, Pythagoras.
Secondly, The Magnetic Flux Is Already Acting Perpendicularly On The Conductor.

 

[Gecko888]

The right hand palm rule for induction means you point your palm in the direction OPPOSING the motion. Thus your palm points towards you.

 

[Sparcod]

Ok. How do you do 7?
Show us the techniques.

 

[shinji]

Ok. How do you do 7?
Show us the techniques.

q7 = direct application of F=BILSin@

where @ = 90 [magnetic field into the page]

u determine the Conductor's length via pythagoras [square magnetic field]
and then use the formulae

 

[slyvester63]

1.C
2.B
3.D
4.D
5.A
6.A
7.C
8.A
9.B
10.D (not sure)
11.A
12.C
13.B
14.B
15.A

These are all my answer.. They questions are not that bad I guess.

 

[Edge_Head]

Can anyone explain Q4? i realise that is simple. But majority is saying B, i just dont see how it is, well i sorta do..... If it was thrown wouldnt that mean that acceleration increases? as it leaves the hand? i dont know, can any one lend some insight to this question??

 

[slyvester63]

For me, i think it wouldn't be possible because after half 't' it cannot stop while moving, the graph actually increasing but then its decreasing...
I think its B because horizontal acceleration is always constant. However still got them wrong

 

[brack777]

For question 9 I found what looks to be the same generator on wiki http://en.wikipedia.org/wiki/Homopolar_generator But it says

"However, unlike all other dynamos, this machine cannot be analysed using Faraday's own law of electromagnetic induction. This law (in its modern form) states that an electric current is induced in a closed electrical circuit when the magnetic flux enclosed by the circuit changes (in either magnitude or direction). However, the circuit in the Faraday disc is parallel to the magnetic flux vector and therefore encloses no magnetic flux. Therefore, Faraday's law does not apply to this machine. Instead, the Lorentz force law is used to explain the machine's behaviour."

If it is not using faraday's law why is it in the exam? lol i got it wrong, i put a

 

[slyvester63]

Yea man.. I heard some generator and other modern stuff can be using laws that are not the same to those we studied in secondary school....

 

[angmor]

th whole fucking multiple choice was a tool..i fucked two up for sure now

 

[helper]

For question 9 I found what looks to be the same generator on wiki http://en.wikipedia.org/wiki/Homopolar_generator But it says

If it is not using faraday's law why is it in the exam? lol i got it wrong, i put a

It can be worked out from Lenz's Law and eddy currents.

 

[theodore]

1. C - g varies according to Gm/r2 and G is the universal gravitation constant

2. B - when the centripetal force of the string is removed, the mass will move horizontally perpendicular to its centre of motion.

3. D - M-M experiment shows the constancy of speed of light which provides evidence for Einstein's theory of relativity

4. B - The only acceleration on a projectile is gravity (g) which remains constant

5. D - Using Kepler's ratios

6. A - The wire will rotate around the magnet in a clockwise direction (i think).

7. C - Using F = BIlsin@ where l is route 1.40 squared

8. A - Im not sure whether flux is maximum or minimum at 0 (possibly B)

9. B - Using right hand palm rule where force is in opposite direction of motion of disc. Therfore current runs from Y to X.

10. A - Not sure about this, something about changing magnetic fields

11. A - Braggs used X-ray crystallography/diffraction

12. C - F = qvBsin@ and F = 0 when velocity is parallel

13. D - Metal lattice does not vibrate as frequently so resuistance is decreased

14. C - Aliminum; E = 5000 Vm-1. So we need E = 10000. This occurs for both perspex and copper, but only copper is suitable

15. D - Im not sure on this one either. Using the wavelength we find that the freqeuncy corresponds to maximum KE for aluminium but work function has to be factored in to find maximum KE. ie. KE = hf - work function of metal



Let me know what you think of these answers. Im hoping for 12-13/15

Agree for the most part, except 7, which is D, cause its perpendicular to the magnetic field (NOT at 45 degrees, as you would believe) and 15 is A, aluminium, worked out by using forumlas, (you get frequency as 1.6 and 2.5 eV, hence Al

That is all...

 

[theodore]

Can anyone explain Q4? i realise that is simple. But majority is saying B, i just dont see how it is, well i sorta do..... If it was thrown wouldnt that mean that acceleration increases? as it leaves the hand? i dont know, can any one lend some insight to this question??

Acceleration on earth, we take as a constant 9.8, (yes okay it varies over the earth, but at the point where its droped is a constant), so yes velocity increases, however gravity is always a constant 9.8, and seeing as the graph wanted is an acceleration-time graph, B shows the constant acceleration of gravity, untill it hits the beach, where there is no more acceleration, showing abrupt end...

hope this clears is up for you.

 

[bboyelement]

It can be worked out from Lenz's Law and eddy currents.

please enlighten us helper ...

 

[helper]

please enlighten us helper ...

Try this

 

[dongypro]

these are mine

--------------------------------------------------------------------------------

1.B
2.A
3.C
4.C
5.B
6.B
7.D
8.B
9.A
10.C
11.B
12.A
13.D
14.A
15.C

im aiming for 99 in physics

 

[dunno04]

can anyone mark it...instead of listing it out.
I wanna kno whether it is right or wrong....

=D

 

[XcarvengerX]

Haha BOS has done it again...

Question 7:
If you got B, that's mean you used 0.4m as length and sin45 which is incorrect. (but this is what I got )
If you got C, well, there are two choices here:
1 if you used sin45 BUT use diagonal length (pythagoras stuff)
2 if you used sin90 BUT use 0.4m as length
If you got D, you used sin90 AND diagonal length (pythagoras stuff)

Very interesting question...