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March 29, 2024, 01:13:27 am

Author Topic: VCE Physics Question Thread!  (Read 603243 times)  Share 

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vcestressed

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Re: VCE Physics Question Thread!
« Reply #1785 on: April 23, 2017, 07:39:52 pm »
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quick question. . .  why is that good conductors of  heat do NOT necessarily have high specific heat capacity?

Syndicate

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Re: VCE Physics Question Thread!
« Reply #1786 on: April 23, 2017, 07:49:16 pm »
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quick question. . .  why is that good conductors of  heat do NOT necessarily have high specific heat capacity?

They are both different things. Good conductors refers to how much heat can the substance absorb, whereas specific heat capacity refers to the amount of joules of energy required to raise the substance's temperature by 1C. ie. Copper is a good conductor of heat, but it's specific heat capacity is only 0.385 J C^-1 g^-1
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Rusten

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Re: VCE Physics Question Thread!
« Reply #1787 on: May 01, 2017, 07:31:35 pm »
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We got a questions asking:

If the Moon were to be put into a new orbit of twice its current radius, what would its potential energy (increase, decrease, no change).

My teacher is saying increase, because E=mgh and double height means double energy... However, given that gravitational fields fall under the inverse square law, would it not be the case that doubling the radius would mean 1/4 of the original 'g' value (grav field strength). Hence, subbing it back into E=mgh, you'd end up with HALF of what the original energy was, not double. Am I missing something here? Thanks in advance.
« Last Edit: May 07, 2017, 05:35:13 pm by jamonwindeyer »

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Re: VCE Physics Question Thread!
« Reply #1788 on: May 01, 2017, 07:39:31 pm »
+2
We got a questions asking:

If the Moon were to be put into a new orbit of twice its current radius, what would its potential energy (increase, decrease, no change).

My teacher is saying increase, because E=mgh and double height means double energy... However, given that gravitational fields fall under the inverse square law, would it not be the case that doubling the radius would mean 1/4 of the original 'g' value (grav field strength). Hence, subbing it back into E=mgh, you'd end up with HALF of what the original energy was, not double. Am I missing something here? Thanks in advance.
Firstly, the inverse square law is related to Newton's Law of Universal Gravitation, i.e. \(F=\frac{Gm_1m_2}{d^2} \). F is an attractive "force". Not the work done.


« Last Edit: May 07, 2017, 05:35:22 pm by jamonwindeyer »

-273.15

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Re: VCE Physics Question Thread!
« Reply #1789 on: May 07, 2017, 04:59:03 pm »
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I don't understand how the formula Ek=GMm/2R is derived from Ek=1/2mv^2, GMm/r^2 and mv^2/r
Could someone please show me how the formula is obtained??

Thanks :)
« Last Edit: May 07, 2017, 05:35:30 pm by jamonwindeyer »

Shadowxo

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Re: VCE Physics Question Thread!
« Reply #1790 on: May 07, 2017, 09:24:15 pm »
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I don't understand how the formula Ek=GMm/2R is derived from Ek=1/2mv^2, GMm/r^2 and mv^2/r
Could someone please show me how the formula is obtained??

Thanks :)

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Re: VCE Physics Question Thread!
« Reply #1791 on: May 08, 2017, 12:59:50 am »
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Hi!

QQ. How can you improve a DC generator? (suggestions of improvement)
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-273.15

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Re: VCE Physics Question Thread!
« Reply #1792 on: May 09, 2017, 07:22:43 pm »
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I was doing a vcaa question from the 2014 exam and you had to describe the direction of the current on a particular section of coil in a DC motor before during and after a quarter turn. I'm confused as i thought the split ring commutator reverses the direction of the current after each half turn, not every quarter turn?

Also could someone explain why there is no current flow before it reverses direction?

Thank you :)
« Last Edit: May 09, 2017, 09:31:44 pm by -273.15 »

Gogo14

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Re: VCE Physics Question Thread!
« Reply #1793 on: May 10, 2017, 04:04:20 pm »
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Hi!

QQ. How can you improve a DC generator? (suggestions of improvement)
Having stronger magnets, a longer coil, more coils, more planes of coils, more split rings, more efficient brushes(e.g. More smooth carbon brushes)

I was doing a vcaa question from the 2014 exam and you had to describe the direction of the current on a particular section of coil in a DC motor before during and after a quarter turn. I'm confused as i thought the split ring commutator reverses the direction of the current after each half turn, not every quarter turn?

Also could someone explain why there is no current flow before it reverses direction?

Thank you :)
a full turn =360degrees, a quater turn =90 degrees nad hence there would not a magnetic force generated as the current is runnign parallel to the magnetic field. There is no current because at every 1/4 turn, the split ring commutator is split. This means that the wires are not in contact with teh commutation, but the split (gap). Hence there is no complete circuit and thus no current
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Re: VCE Physics Question Thread!
« Reply #1794 on: May 21, 2017, 12:12:53 am »
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A block on the table is accelerated by a falling weight. Calculate the tension in the cord if the block experiences a frictional force of 1.5N as it slides on the table (blockA=2.0kg, blockB=0.5kg)

Answer is 4.3N
How?!?!????
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Logic

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Re: VCE Physics Question Thread!
« Reply #1795 on: May 21, 2017, 09:06:34 pm »
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Where's everyone up to in the course btw?

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Re: VCE Physics Question Thread!
« Reply #1796 on: May 21, 2017, 11:15:47 pm »
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Where's everyone up to in the course btw?
Howdy, I'm starting special relativity tomorrow :D
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mouldycarrots

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Re: VCE Physics Question Thread!
« Reply #1797 on: May 22, 2017, 07:55:13 pm »
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Where's everyone up to in the course btw?
We're doing transformers and transmission at the moment

princessofpersia

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Re: VCE Physics Question Thread!
« Reply #1798 on: May 22, 2017, 08:15:47 pm »
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Where's everyone up to in the course btw?

we're currently doing circular motion on vertical planes

princessofpersia

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Re: VCE Physics Question Thread!
« Reply #1799 on: May 22, 2017, 08:30:12 pm »
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A block on the table is accelerated by a falling weight. Calculate the tension in the cord if the block experiences a frictional force of 1.5N as it slides on the table (blockA=2.0kg, blockB=0.5kg)

Answer is 4.3N
How?!?!????


Fnet on system= (0.5 x 10) - 1.5 (friction)
=3.5N
Acceleration of 2.0kg............3.5N/(2kg+0.5kg)= 1.4m/s^2
Fnet on block= Tension + friction
mass x acceleration= tension -1.5
2.8= tension -1.5
tension = 4.3N