C4 volume question

TSRforum

Confused on how to approach this question :/ ImageUploadedByStudent Room1464112511.745871.jpg

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Reply 1

Nayzar

wth lol. just out of interest what exam board is that from?

Reply 2

zetamcfc

Original post by TSRforum

Confused on how to approach this question :/ ImageUploadedByStudent Room1464112511.745871.jpg

Posted from TSR Mobile

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?

Reply 3

TSRforum

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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Reply 4

zetamcfc

Original post by TSRforum

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.

Reply 5

TSRforum

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.

Here's the answer: ImageUploadedByStudent Room1464118924.721022.jpg

Don't really see how I can sketch that or even work out the limits from looking at it.

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Reply 6

zetamcfc

Original post by TSRforum

Here's the answer: ImageUploadedByStudent Room1464118924.721022.jpg

Don't really see how I can sketch that or even work out the limits from looking at it.

Posted from TSR Mobile

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.

Reply 7

TSRforum

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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Reply 8

zetamcfc

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.

Reply 9

TSRforum

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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Reply 10

zetamcfc

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, volume..png

(ignore the top half of the circle.)

Reply 11

TSRforum

Original post by zetamcfc

The axes are arbitrary, you just need to be able to see how one corresponds with the other, volume..png

(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 :smile: