# IB Physics help

Thread starter 3 years ago
#1
guys it would be great if we could help each other with Physics, whether it's at GCSE level, IB or A-levels.
I'm struggling loads after all so I think team-work and support is the best solution, not only for me but for you too!
After all, teaching is the most efficient way to learn!
0
3 years ago
#2
What do you need help with.
0
Thread starter 3 years ago
#3
hi!! hahah everything, but with the waves topic to start with, I guess. It's mostly applying my knowledge to practice questions that I find the hardest, I think.
(Original post by Levi23317)
What do you need help with.
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3 years ago
#4
If theres any questions you want help with im happy to help
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Thread starter 2 years ago
#5
Hi,
I don't understand the inverse square law - at all. Like I get that it means that if the distance doubles then the intensity quadruples or something idk but... Any help please?

(Original post by Levi23317)
If theres any questions you want help with im happy to help
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2 years ago
#6
(Original post by mikaelalrc)
Hi,
I don't understand the inverse square law - at all. Like I get that it means that if the distance doubles then the intensity quadruples or something idk but... Any help please?
So the inverse square law in terms of intensity refers to the power per unit area from a a wave source that is emitting waves equally in all directions. So if you picture an expanding sphere whos centre is the wave source e.g core of a star, it expands, so the power for a given area decreases the further away you are since the sphere is larger. Since its a sphere the intensity (power per unit area) is p/4piR^2 , as 4piR^2 is the surface area of a sphere. Therefore intensity is inversely proportional to the separation from the centre of the source (radius) squared.
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2 years ago
#7
The waves topic is a personal favorite of mine! If you have any questions send them
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2 years ago
#8
(Original post by JasmineLLB)
The waves topic is a personal favorite of mine! If you have any questions send them
Yo me are we like best friends or somethin
0
Thread starter 2 years ago
#9
Thank you! But I still don't quite understand it... It's the maths that confuses me. And what does inversely proportional mean again?
(Original post by Levi23317)
So the inverse square law in terms of intensity refers to the power per unit area from a a wave source that is emitting waves equally in all directions. So if you picture an expanding sphere whos centre is the wave source e.g core of a star, it expands, so the power for a given area decreases the further away you are since the sphere is larger. Since its a sphere the intensity (power per unit area) is p/4piR^2 , as 4piR^2 is the surface area of a sphere. Therefore intensity is inversely proportional to the separation from the centre of the source (radius) squared.
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2 years ago
#10
(Original post by mikaelalrc)
Thank you! But I still don't quite understand it... It's the maths that confuses me. And what does inversely proportional mean again?
Y is inversely proportional to X:
where k is some constant, doesn't matter. So as X gets bigger, Y gets smaller - because you're dividing by a bigger number.
So if X is made twice as big, Y is made half the size.

Y is inversely proportional to the square of X - aka inverse-square relationship:

Same rule - as X gets bigger, Y gets smaller - but it happens a lot quicker. So if X doubles, Y is reduced 4 times. If X is tripled, Y is reduced 9 times. Substitute 3X and square it, and you'll see.

Y is directly proportional to X:

So Y linearly increases with X. Y is always k times the size of X. The ratio between Y and X is always k.

Y is proportional to the square of X:

Y increases with the square of X. Make X twice as big, Y will be 4 times as big. Make it 4 times as big, Y will be 16 times as big.
Last edited by Sinnoh; 2 years ago
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2 years ago
#11
(Original post by mikaelalrc)
Thank you! But I still don't quite understand it... It's the maths that confuses me. And what does inversely proportional mean again?
Its means 1 over something.so if something is inversely proportional to R^2 , it is directly proportional to 1/R^2
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Thread starter 2 years ago
#12
thank you, i think i get that now!
(Original post by Levi23317)
Its means 1 over something.so if something is inversely proportional to R^2 , it is directly proportional to 1/R^2
0
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