#### Bug

##### New Member
What did you get, this is what I got:
1 B
2 A
3 B
4 B
5 D
6 A
7 A
8 C
9 C
10 B
11 A
12 C
13 C
14 B
15 A

NB: WHat did you think of the Quanta to quarks question ??

#### hk*star

##### New Member
haha damn i think i made up half of them
mc was the hardest part of the test
is copper magnetic??
yeah i only got 1 d as well for answer

#### josie_is_slut

##### Member
i think i stuffed it badddd
i got a ombination of a, b, and c' , no d's

1.B
2.B
3.B
4.B
5.A I used the wrong radius
6.A
7.A
8.C
9.C
10.A
11.A
12.C
13.C
14.C
15.A

#### BlackJack

##### Vertigo!
Don't know about 6-9 but I remember the other questions matching...
(btw, I think there's only 1 D)

#### AlexZ

##### New Member
1. B Acceleration always acts down
2. A Time will run slower and length will contract
3. B Obvious...
4. B Obvious..
5. D I got the wrong answer first, then fixed it and got this. I'm sure this is right.

6. A Obvious..
7. A formula...
8. C
9. C
10. B Yup, i'm sure about this one as welll. It's between B and D and D is way off...

11. A
12. C
13. C
14. B This is the correct answer
15. A

Yeah, so those are mine, and i'm basically 1000% sure all of them are right.

#### spice girl

##### magic mirror
i agree with AlexZ

#### EXA BOY

##### Member
if ur right i got 3 wrong.... not 2 bad qn 5 i swear is A cause r^3/T^2 = k so i ended up wiv a.... qn 6 i made a stupid mistake and said B even though i answered the other transformer qn right... then qn 10 i didnt know wat the answer was and i went for A..... so 3 wrong if ur right dude

#### Bug

##### New Member
Q5.

Alif:
T = 8.75 x 10^7
r = 4.00 x 10^11

=> r^3 / T^2 = k
thus, k = 8.359 x 10^18

Ba:
T = ?
r = 8.00 x 10^11
k = 8.359 x 10^18

using: r^3 / T^2 = k
=> T = sqr(r^3 / k)
thus, T = 2.47 x 10^8

#### EXA BOY

##### Member
qn 5 is DEFINATELY A my mum just came home (shes a chem teacher at JR and asked me if i got A for dat question cause the physics teacher there said its DEFINATELY A) by the way i just said, all u do is say r^3/T^2=k u work out the k from the info they gave u on the planet in the tabel, then work out T for the second planet now that u know R and K

#### McLake

##### The Perfect Nerd
12/15 if I trust AlexZ and Spice Girl ...

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#### EXA BOY

##### Member
bug i think u stuffed it cause u used ORBITAL radius, not radius of planet??? maybe the physics teacher got it wrong though?!?!?! im sure its A though
Actually Bug..... after all dat i think u r right.... but now im just confused... ummmmm i think im wrong ppls hahahaha oh well watcha gonna do.... simple error

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#### Bug

##### New Member
Your ment to use orbital radius, the size and mass of the planet has no relavence.

It's twice as far away, so Ba is gonna take longer to orbit the star then Alif is - thus A and B are excluded.

#### kaseita

##### Member
I got q4 wrong. textbook question, but forgot whether it was Q or R
good enough I reckon. I could've done worse (I have before!)

#### Lazarus

##### Retired
Hello... could one of you nice people explain how you deduced that B was the answer for Q10?

This was my reasoning...
emf = ΔΦ/Δt

Initially, there is no flux, as the coil is parallel to the magnetic field (the plane of the coil is not cutting any field lines). Then the coil rotates 90 degrees clockwise and so there is a positive change in flux and hence an induced emf. The coil rotates another 90 degrees clockwise and there is a negative change in flux and hence an induced emf in the opposite direction. And so on for the next two quarter-turns.

It's an AC generator, so it's being manually rotated, and the movement I described would match with the commutator... (I think)

Why isn't it C? I suspect I'm doing something silly.

#### ske

##### New Member
eeep!..

why iznt 2 b?..like i was tossin up between a n b but doesnt time run faster on the SPACESHIP..?...coz from his perspective time is dilated for him?...coz i alwaiz thot it was the external observer that is dialated..but then again relativity works both ways ><..eh..som1 plz explain..

n for 4..iznt it c..coz at q gforce = 1g?..well eh..otha than that mah answers seem to match..

#### BlackJack

##### Vertigo!
It starts with a velocity perpendicular to the magnetic field... max emf...
at 90 degrees, the sides of coil is moving parallel to mag field... zero emf...
used tangential velocity on the coil.

#### Lazarus

##### Retired
but blackjack, wouldn't that be induced current, not induced emf?

or are they the same thing? i've not heard that before. I thought emf was a potential difference. or something. been a while.

#### BlackJack

##### Vertigo!
emf IS potential difference but should be equivalent to current in this question. If there's no Voltage then there's no current... voltgage, then there must be current...
that's my reasoning.

#### Lazarus

##### Retired
emf is a potential difference but it's not a voltage (it's not conservative)

you can have an emf in an open circuit.

Grr. I have a physics exam in 2 weeks as well, I should be able to do this stuff.