OCR Physics A G484 - The Newtonian World - 11th June 2015 Watch

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(Original post by Username13)
Can someone explain specific heat capacity please?
If there's a lower specific heat capacity, why does temperature of the object fall more quickly?
Imagine SHC as the ability for an object to retain heat
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Hilton184
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#402
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(Original post by Username13)
Can someone explain specific heat capacity please?
If there's a lower specific heat capacity, why does temperature of the object fall more quickly?
Specific heat capacity is the energy required to raise the temperature of a unit mass of a substance by a unit temperature rise.

So a substance with a higher c value requires more energy to raise its temperature by value x.
A substance with a lower c value requires less energy to raise its temperature by value x.

Hence substance c will cool quicker because as energy is lost, there is a greater temperature decrease per unit time.


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ForgottenApple
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#403
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(Original post by Hilton184)
Specific heat capacity is the energy required to raise the temperature of a unit mass of a substance by a unit temperature rise.

So a substance with a higher c value requires more energy to raise its temperature by value x.
A substance with a lower c value requires less energy to raise its temperature by value x.

Hence substance c will cool quicker because as energy is lost, there is a greater temperature decrease per unit time.


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Assuming they lose it at the same rate?
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Username13
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(Original post by Hilton184)
Specific heat capacity is the energy required to raise the temperature of a unit mass of a substance by a unit temperature rise.

So a substance with a higher c value requires more energy to raise its temperature by value x.
A substance with a lower c value requires less energy to raise its temperature by value x.

Hence substance c will cool quicker because as energy is lost, there is a greater temperature decrease per unit time.


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(Original post by [email protected])
Imagine SHC as the ability for an object to retain heat
Thank you
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Makashima
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#405
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Hey guys, whats your definition for centripetal force...I dont remember seeing it asked in the exam so it wasnt on the MS? Hmmm mines sounds very plain and probably wont gain any marks?

The resultant force towards the centre of the circular motion at 90 degree to the velocity...
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Elcor
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(Original post by Makashima)
Hey guys, whats your definition for centripetal force...I dont remember seeing it asked in the exam so it wasnt on the MS? Hmmm mines sounds very plain and probably wont gain any marks?

The resultant force towards the centre of the circular motion at 90 degree to the velocity...
When a resultant force is perpendicular to an object's velocity it will make the object describe a circular path.
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ForgottenApple
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(Original post by Elcor)
When a resultant force is perpendicular to an object's velocity it will make the object describe a circular path.
I would say when it always acts perpendicular.
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randlemcmurphy
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(Original post by ForgottenApple)
I would say when it always acts perpendicular.
:sigh:
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ForgottenApple
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(Original post by randlemcmurphy)
:sigh:

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verello12
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Quesiton 3c on Jan 2011 paper, I don't understand why the line going from 0C to -18C is suppose to be steeper than the line going from 18C to 0C. I thought If the specific heat capacity is lower then the substance will cool down slower resulting in a more shallow gradient but apparently that's incorrect

EDIT: Nevermind if specific heat capacity is lower it means that when an object is cooling it needs to give off less energy therfore it'll take a shorter amount of time which means steeper gradient. I get it now
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sagar448
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(Original post by verello12)
Quesiton 3c on Jan 2011 paper, I don't understand why the line going from 0C to -18C is suppose to be steeper than the line going from 18C to 0C. I thought If the specific heat capacity is lower then the substance will cool down slower resulting in a more shallow gradient but apparently that's incorrect
No you see, if the specific heat capacity is lower than the substance cools down faster because with a lower specific heat capacity it means it needs less energy to raise it's temperature so therefore since it does not have a lot of heat energy it will cool down faster (because of surrounding temperature; high contrast to low contrast). That is why it is steeper.
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verello12
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Q4biii Jan 2011 how we know is we should use x=Asin(2pieft) or x=Acos(2pieft), it doesn't tell us if time was started at a high/low tide or the midpoint of the tide, although in the mark scheme it does say accept sin or cos but wouldn't that make a big difference
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sagar448
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(Original post by verello12)
Q4biii Jan 2011 how we know is we should use x=Asin(2pieft) or x=Acos(2pieft), it doesn't tell us if time was started at a high/low tide or the midpoint of the tide, although in the mark scheme it does say accept sin or cos but wouldn't that make a big difference
Its fine, you can use either sin or cos. They allow this because you're not doing any calculating with it, they just wanted an expression.

But in a SHM question if the pendulum or spring-mass is released from max amplitude then use cos, if it is released from equilibrium position then use sin.

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verello12
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(Original post by sagar448)
Its fine, you can use either sin or cos. They allow this because you're not doing any calculating with it, they just wanted an expression.

But in a SHM question if the pendulum or spring-mass is released from max amplitude then use cos, if it is released from equilibrium position then use sin.

Thank you
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Hilton184
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(Original post by ForgottenApple)
Assuming they lose it at the same rate?
Yes assuming that they lose it at the same rate, which would depend on the surface area and probably other factors? What other factors would effect this? Or is it only surface area?


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BrokenS0ulz
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So does the gravitational field strength always equal the acceleration of an object due to the gravitational field at all distances?
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Elcor
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(Original post by BrokenS0ulz)
So does the gravitational field strength always equal the acceleration of an object due to the gravitational field at all distances?
Yeah as long as there are no other forces.
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BrokenS0ulz
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When we have to work out the area under a F/t graph to get the impulse, what do most of you guys do? Do you count the squares or try and split it into shapes?
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BrokenS0ulz
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(Original post by Elcor)
Yeah as long as there are no other forces.
Thank you
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Shabz12357876877
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am i the only one thats pretty much stuck on my mark? im not improving and im not sure why like i know the definitions and stuff better now but im still only getting like 3 marks above an a in pretty much all my papers (sometimes lower) i dont do maths and its those mathematical questions that put me off ( the resultant velocities and stuff) ive ran out of past papers does anyone have any sites / tips on what i can do to revise? i struggle on explanations and maths and i dont think i have a physicists mentality (i cant think outside the box with many questions like the one where it asks about the sand grains on the stereo )
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