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March 29, 2024, 03:59:31 pm

Author Topic: VCE Physics Question Thread!  (Read 603451 times)  Share 

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Yacoubb

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Re: VCE Physics Question Thread!
« Reply #600 on: September 17, 2014, 11:55:58 pm »
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Your working missed a nuance in the question. The question says 'speed v'. But it's returning downwards, so its final velocity is actually -v, not v.

Ah yes, I see. Thanks lzxnl!

maurlock

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Re: VCE Physics Question Thread!
« Reply #601 on: September 21, 2014, 01:01:16 pm »
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Why is the cosine angle used in this question instead of sine?
Thanks!

Conic

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Re: VCE Physics Question Thread!
« Reply #602 on: September 21, 2014, 02:01:40 pm »
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The angle used in the formula is the angle between the force and the lever. In this case, as the angle with the ground is 65, the angle with the lever is 25, so the torque is given by



which means that E is correct. Because it appears that the cosine of the angle is used, but you need to make sure you use the right angle. The cosine of the angle with the ground happens to be equal to the sine of the angle between the weight force and the lever, which is what is actually used in the calculation.
« Last Edit: September 21, 2014, 02:03:17 pm by Conic »
2012-13: VCE at Parade College (Chemistry, English, Mathematical Methods, Physics and Specialist Mathematics).
2014-16: Bachelor of Science at La Trobe University (Mathematics and Statistics).
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maurlock

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Re: VCE Physics Question Thread!
« Reply #603 on: September 22, 2014, 05:50:39 pm »
+1
The angle used in the formula is the angle between the force and the lever. In this case, as the angle with the ground is 65, the angle with the lever is 25, so the torque is given by



which means that E is correct. Because it appears that the cosine of the angle is used, but you need to make sure you use the right angle. The cosine of the angle with the ground happens to be equal to the sine of the angle between the weight force and the lever, which is what is actually used in the calculation.
Oooh I see, thank you so much!

speedy

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Re: VCE Physics Question Thread!
« Reply #604 on: September 23, 2014, 05:01:06 pm »
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Why is Fbox on trailer > Ftrailer on box?
Spoiler
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Yacoubb

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Re: VCE Physics Question Thread!
« Reply #605 on: September 23, 2014, 06:15:52 pm »
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Why is Fbox on trailer > Ftrailer on box?
Spoiler

I could be wrong, but I think you're not looking at the diagram correctly. The arrow from the trailer upwards is actually from the bottom of the box (where the trailer makes contact with the box), and the arrow downwards is from the bottom of the trailer downwards, so in reality the proportion of upwards to downward arrow size is the same. It would have to be according to Newton's 3rd Law of Motion...

speedy

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Re: VCE Physics Question Thread!
« Reply #606 on: September 23, 2014, 06:42:25 pm »
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I could be wrong, but I think you're not looking at the diagram correctly. The arrow from the trailer upwards is actually from the bottom of the box (where the trailer makes contact with the box), and the arrow downwards is from the bottom of the trailer downwards, so in reality the proportion of upwards to downward arrow size is the same. It would have to be according to Newton's 3rd Law of Motion...

Well I just drew that on so idk. I guess it comes down to interpretation of the image in the question:
Spoiler

If we say that the box is within the trailer, then I agree with you. If we say that it just sits on top then clearly the arrow downwards is larger. I don't know why the answer doesn't show both the trailer and box - makes the origin very ambiguous.

When I did the question I took it to be sitting on top of the trailer (see diagram), but I upon looking at it again, it does appear to go deeper.
« Last Edit: September 23, 2014, 06:45:08 pm by speedy »
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allstar

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Re: VCE Physics Question Thread!
« Reply #607 on: September 23, 2014, 06:55:02 pm »
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for the gain of an amplifier, (even if it is an inverting amplifier), should it always be a positive value?

Zealous

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Re: VCE Physics Question Thread!
« Reply #608 on: September 23, 2014, 07:02:12 pm »
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for the gain of an amplifier, (even if it is an inverting amplifier), should it always be a positive value?
I quite sure that as long as you take the gradient of the Vin/Vout graph, whether negative or positive VCAA will accept it (from the assessment reports I've seen). I usually just take the magnitude anyway though - negative gain just sounds awkward.
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Yacoubb

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Re: VCE Physics Question Thread!
« Reply #609 on: September 23, 2014, 07:28:24 pm »
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I quite sure that as long as you take the gradient of the Vin/Vout graph, whether negative or positive VCAA will accept it (from the assessment reports I've seen). I usually just take the magnitude anyway though - negative gain just sounds awkward.

Yeah I always just find the absolute value. Negative gain...it does sound awkward lol.

allstar

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Re: VCE Physics Question Thread!
« Reply #610 on: September 23, 2014, 07:31:00 pm »
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thank you guys!

just another one:
Can a light dependant resistor be used as a demodulator?
i know LED are used for the modulator

Yacoubb

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Re: VCE Physics Question Thread!
« Reply #611 on: September 23, 2014, 07:31:57 pm »
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thank you guys!

just another one:
Can a light dependant resistor be used as a demodulator?
i know LED are used for the modulator

Yep! :-)

allstar

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Re: VCE Physics Question Thread!
« Reply #612 on: September 23, 2014, 07:38:55 pm »
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but the ans says i can't? why?

Yacoubb

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Re: VCE Physics Question Thread!
« Reply #613 on: September 23, 2014, 07:43:03 pm »
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but the ans says i can't? why?

Does it say photodiode?

allstar

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Re: VCE Physics Question Thread!
« Reply #614 on: September 23, 2014, 07:49:17 pm »
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it just says no?

i dunno probably just another dodgy question

can i ask another one?

what is the purpose of slip rings in AC generator?