VCE Physics Question Thread!

[Thu Thu Train]

The answer you have gotten is correct. One upside of physics is that there often aren't very many technicalities to a question, it's just a matter of plugging numbers in.

[Stevensmay]

Lets be honest here, this is VCAA style physics.
The only thing that has some degree of 'better watch out for that' I find is light.
Motion is essentially 'I've got these letters, let me look at my cheatsheet to see which formula has them.'
Electronics is 'can I read a graph, a formula and use V=IR.'

Light actually takes some learning, but only because VCAA tend to ask more theory orientated questions.

[lolipopper]

Lets be honest here, this is VCAA style physics.
The only thing that has some degree of 'better watch out for that' I find is light.
Motion is essentially 'I've got these letters, let me look at my cheatsheet to see which formula has them.'
Electronics is 'can I read a graph, a formula and use V=IR.'

Light actually takes some learning, but only because VCAA tend to ask more theory orientated questions.

i havent dropped a single mark for any unit 4 exam that i have done for physics. However i tend to drop 1 or 2 marks on the tension and relative motion questions for Unit 3. This is why only a quarter of my summary sheet is light and matter and electricity.The rest is motion.

[Robert123]

Thanks for the response
I knew that vicphysics solutions has some other errors in their answer but when I check itute and they both have the same answer, it threw me off completely

[lolipopper]

quick question:

is relative motion still in Unit 3?
and also are the specific properties of materials to be known in "Detailed study : Materials and Structure"

[Alwin]

This satellite question is driving me crazy!!
Q8 of motion in the 2013 sample exam by VCAA
R=1.35*10^7m
G=6.67*10^-11
M (earth)=5.98*10^24kg
m (satellite)=525kg
What is the period?
Both Vicphysics and Itute answer say it is1.53*10^4s but whenever I do it I always get 1.56*10^4s. It is so close yet so far away, could someone please test this question, I know how to do it but it just isn't working.

Oh this question VCAA copy + pasted that q from the 2009 exam iirc, but changed the numbers. SO the solutions companies posted up were wrong too because they copied their solutions from 2009 too lol

here, from a set of 'model' solutions I made myself for the 2013 practice exam :



@lollipopper: when I did physics last year it wasn't, I think it was in Special Relativity detail study for some reason (apparently too hard for normal physics students?). And I don't recall there being any specifics needed to be rote learned for Materials I think. If there are you don't even need to learn it, just chuck it on your cheat sheet if anyone knows what needs to be memorised this year (sorry, it's been over a year and a half for me since materials so forgotten heaps =\)

[Jaswinder]

how to do 1b from 2012 Exam 2? About the orientation the magnet will take?

[sin0001]

Does it matter where you place the diode in a series circuit?

For example, you have the positive end of supply connected to reverse biased diode then diode connected to resistor then resistor connected back to supply.
The entire voltage supply drops across the diode as no current flows through it hence no drop across resistor.

But how about if the position of the diode and the resistor are swapped? Would the same thing happen?
What happens to the current that flows across the resistor first?

Current would first pass through the resistor, resulting in a drop, and THEN it'll be stopped by the diode in reverse-biased.

[sin0001]

If the current passes through the reverse biased diode first, all 6 volts of the supply would dropped across it, meaning there will be NO drop across the resistor

[Robert123]

But what I'm asking is what if the current flows through the resistor first, then the reverse biased diode stops the current flow?

For the current to flow, you would need a complete circuit (ie doesn't flow in one half then stops)
Assuming the reverse bias diode has no leakage current, it would probably just act like an incomplete circuit.
The best way to find out is just to actually test it in real life.

[SocialRhubarb]

No current flows if you have a diode in reverse bias anywhere in a series circuit.

Robert123 is right - the diode in reverse bias would act just like a break in the circuit.

You can't have current flowing halfway through a circuit and then stopping.

[SocialRhubarb]

Okay, I don't actually do structures and materials so there may be an easier way to do this, but here goes:

I think in this case it may actually be helpful to at least think of the force diagram. There are three forces involved here - the force from the rod, the force from the wire and the weight force of the lamp, and we want the lamp to have a net force of 0. Now, which ways are the forces acting?

Weight force is quite simple, obviously straight down. But the rod is being compressed, so will be exerting a force diagonally upwards on the lamp, while the wire is in tension, so will be exerting a force to the left.

If we resolve these forces, the vertical component of the rod's force must balance out the lamp's weight force, and the horizontal component of the rod's force must balance out the tension in the string.

Spoiler

[Jaswinder]

how to do 1b from 2012 Exam 2? About the orientation the magnet will take?

bumb

[Thu Thu Train]

bumb

Figure out the where the 'north' and 'south' end of the solenoid is. Your smaller magnet will act as a compass needle which(without any other magnetic fields) points at magnetic north. Placing the magnet near point Q and allowing it freely rotate means that the north end of the magnet will rotate to face the south end of the solenoid.

Spoiler

(the answer is C)

[Jaswinder]

Figure out the where the 'north' and 'south' end of the solenoid is. Your smaller magnet will act as a compass needle which(without any other magnetic fields) points at magnetic north. Placing the magnet near point Q and allowing it freely rotate means that the north end of the magnet will rotate to face the south end of the solenoid.

Spoiler

(the answer is C)

wouldn't the magnetic field of earth have any effect on it?