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VCE Physics Question Thread!

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LazyZombie:

--- Quote from: Robert123 on April 17, 2013, 04:05:36 pm ---General questions about voltage;
Why can you have negative voltage (AC) ? Doesn't that imply we can have "negative" energy? Wouldn't it be best if we have negative and positive current for saying which way the current flow?
Also;
I lost a mark on a SAC with the question being about explainging how seatbelt and crumpling reduce the severity of the drivers injury, it was a 3 mark question. What type of exam "style" answers should I have. The teacher noted on it "how does the seat belt increase the time of collision?", how would I undergo answering that for an 'exam' quality answer?
Thanks :)

--- End quote ---
I'm not sure about the voltage thing but since voltage is relative, I think it is possible. But I'm prettyy sure its not necessary in the course. (not in the study design) I might get back to this later :)

As for the crumple zone and seatbelt
therefore the crumble zone increases the time of the collision, thus decreasing the force.
Inertia causes the body to continue moving in the original motion of the car in a collision and cause injury or fatality, and seatbelts help to prevent this from happening.

Seatbelts don't increase the time of collision. I think that's what your teacher means. (?)

availn:
Put simply, if voltage is negative, then the current is also negative. As P = VI, the negative cancels out.

And yeah, seat belts aren't crumple zones, they don't increase the time of collision, they just make sure you don't shoot out of your car.

Lasercookie:

--- Quote from: Robert123 on April 17, 2013, 10:35:45 pm ---Ok, thanks for that. I will ask my teacher what her opinion of what the answer "should" be (even though I find people on this forum more knowledgable and reliable with answer).
Also, another question (this is more a general education question).
Does the only thing that matters with SACs is your ranking? Please only answer if you are 100% sure due to reading a report from VCAA or talking to an examiner?
If so, then does that means there is no different between averaging  90% and 100% on SACs if you go to a low scoring school?

--- End quote ---
Split this post and moved it to the Technical Score Discussion boards

[paradox]+:
Jasper has a transistor radio with flat batteries. Suggest a reason to explain why the sound is distorted when he tunes in to a strong radio signal.

^help anyone? thanks in advance

~T:

--- Quote from: [paradox]+ on April 25, 2013, 04:41:12 pm ---Jasper has a transistor radio with flat batteries. Suggest a reason to explain why the sound is distorted when he tunes in to a strong radio signal.

^help anyone? thanks in advance


--- End quote ---
I'm not entirely sure on this one but I'll give you my thoughts...

Basically, any amplification system works of a small varying AC signal (the radio signal here) and a larger DC input (the battery here) that amplifies the input signal to create a much larger output (the sound here).

So, if the batteries are running flat, then they will not supply enough power to the transistor(s) in order to amplify the larger voltages, and the linear amplification region may be smaller. The input voltages will still be the same, but the extreme values will no longer be amplified linearly, distorting the signal.

This only half makes sense in my head. But pretty much, there is no reason that the input signal would be larger (resulting in clipping outside of the region) so it must be that the linear region itself becomes smaller.

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