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# C4 volume question

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1. Confused on how to approach this question :/

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2. wth lol. just out of interest what exam board is that from?
3. (Original post by TSRforum)
Confused on how to approach this question :/

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Ok so what we need is a function to be integrated.

Consider the equation, (x-r)^2 +y^2 =r^2 (perhaps sketch it)

How might that help?
4. (Original post by zetamcfc)
Ok so what we need is a function to be integrated.

Consider the equation, (x-r)^2 +y^2 =r^2 (perhaps sketch it)

How might that help?
How would I sketch that? Also I can see it can be re-arranged to y^2=.... as whatever I am integrating needs to be squared and multiplied by pi though I still don't know what the limits should be.

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5. (Original post by TSRforum)
How would I sketch that? Also I can see it can be re-arranged to y^2=.... as whatever I am integrating needs to be squared and multiplied by pi though I still don't know what the limits should be.

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At C4 you should be able to sketch a circle. You will be able to see what the limits are once you have sketched it. http://www.wolframalpha.com/ if you really can't sketch.
6. (Original post by zetamcfc)
At C4 you should be able to sketch a circle. You will be able to see what the limits are once you have sketched it. http://www.wolframalpha.com/ if you really can't sketch.
Don't really see how I can sketch that or even work out the limits from looking at it.

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7. (Original post by TSRforum)
Don't really see how I can sketch that or even work out the limits from looking at it.

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You can see how the sketch relates to the question as if you rotate that curve with R at the bottom you see it is like the picture in the question, the limits would follow from that.
8. (Original post by zetamcfc)
You can see how the sketch relates to the question as if you rotate that curve with R at the bottom you see it is like the picture in the question, the limits would follow from that.
Do I look at the bowl from a birds eye perspective?

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9. (Original post by TSRforum)
Do I look at the bowl from a birds eye perspective?

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No, from front on so you see a half circle with a shaded area.
10. (Original post by zetamcfc)
No, from front on so you see a half circle with a shaded area.
Then do I rotate it 90 degree clockwise so it fits the x and y axis chart?

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11. (Original post by TSRforum)
Then do I rotate it 90 degree clockwise so it fits the x and y axis chart?

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The axes are arbitrary, you just need to be able to see how one corresponds with the other, (ignore the top half of the circle.)
12. (Original post by zetamcfc)
The axes are arbitrary, you just need to be able to see how one corresponds with the other, (ignore the top half of the circle.)
Thanks. It's a bit hard to tell what length h covers in relation to r by looking at the pic in the question, this makes everything much clearer

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