Finding volume with polar coordinate.

In summary, the conversation discusses a question about finding the estimated volume of an irregular shape given a set of points with r, theta, and z values. The shape is described as having a hexagonal base and possibly a sand clock shape. The conversation also mentions using Excel VBA and considering a cylinder as a possible shape. However, it is noted that the shape may have changed with the addition of more points. The speaker requests a visual representation of the points for better understanding.
  • #1
isdouble
3
0
The question I have is a bit strange.
I do not have ANY formulas or equations given.
I was only given bunch of points with r, theta, and z. Z being the depth. R being radius and Theta being the angle.
I was wondering if there is a way to find a rough estimate volume of the following.
R Theta Z
0.5 0 0
0.4 60 0.1
0.3 120 0
0.4 180 0.2
0.5 240 0
0.4 300 0
0.5 0 3
0.4 60 3.1
0.3 120 3.1
0.4 180 3
0.5 240 3.2
0.4 300 2.9

Of course I tried using triple integral method but was immediately out the window since there is no equations to input. Any advice would be great. Thank you.
Oh BTW, this is a irregular shape so I cannot link it to any common shapes either..
 
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  • #2
It looks like you have 6 points around the bottom and top. If you look straight down at these points you see an irregular hexagon shape. Are the vertical sides assumed to be flat between the given points like a hexagonal cylinder or are the sides curved and just pass through the six points of the hexagon shape? I'm thinking you could take the area of the hexagon projection times the average height maybe? What else do you know about the shape?
 
  • #3
I got nothing. My prof just gave me these points and told me to find an estimated volume by using Excel VBA but I can't even use the VBA if I can't even solve the problem on paper. She told me there is no right or wrong answer so am I suppose to just guess what it's suppose to be? I was thinking about the same as you but that would be my last choice. Thanks for your input.
 
  • #4
Here's a picture. The scale on the vertical axis is compressed. One could certainly imagine a cylinder like surface.

points.jpg
 
  • #5
That's one part. I forgot to mention the second part. BTW thanks for the drawing. It's really helping. So for part 1, I'm going to assume that its a cylinder and use the volume formula to find it. For part B, there are more points added to the original.
R Theta Z
0.55 0 0.4
0.45 60 0.6
0.35 120 1
0.45 180 0.8
0.55 240 1
0.45 300 1.5
0.45 0 1.9
0.35 60 2.1
0.25 120 2.5
0.35 180 2
0.45 240 2
0.35 300 2
Now it changed the form from cylinder into a irregular shape.
I can kind of visualize it like a sand clock shape. (I think?)
I'm sorry but can you draw these points on top of the ones you drew previously?
That would help me visualize better.
Thank you.
 
  • #6
isdouble said:
Now it changed the form from cylinder into a irregular shape.
I can kind of visualize it like a sand clock shape. (I think?)
I'm sorry but can you draw these points on top of the ones you drew previously?
That would help me visualize better.
Thank you.

This is probably pushing the boundary of how much I should do for you:

points2.jpg


Note that the lines aren't plotted in the order the points are given. You will have to sort that out.
 

1. What is the formula for finding volume with polar coordinates?

The formula for finding volume with polar coordinates is V = ∫∫∫ r sin(θ) dr dθ dθ.

2. How is finding volume with polar coordinates different from finding volume with Cartesian coordinates?

Finding volume with polar coordinates involves using polar coordinates (r and θ) instead of Cartesian coordinates (x, y, and z). The formula also differs, as it takes into account the extra variable of θ, the angle from the positive x-axis.

3. Can you provide an example of finding volume with polar coordinates?

Sure, let's say we have a cone with a radius of 3 and a height of 5. Using polar coordinates, we can express the cone's volume as V = ∫∫∫ r sin(θ) dr dθ dθ, where r ranges from 0 to 3 and θ ranges from 0 to π/2. Plugging in these values, we get V = ∫0π/2 ∫03 ∫03r dr dθ dθ = 45π/8 units cubed.

4. What are some real-world applications of finding volume with polar coordinates?

Finding volume with polar coordinates can be used to calculate the volume of 3D objects with rotational symmetry, such as cones, cylinders, and spheres. It can also be used in engineering and physics to calculate the volume of objects with curved surfaces.

5. Are there any limitations or drawbacks to using polar coordinates to find volume?

One potential limitation is that polar coordinates may not be as intuitive or easy to visualize as Cartesian coordinates for some people. Additionally, some 3D objects may be more difficult to express in polar coordinates, making the calculation of volume more complex. It's important to choose the coordinate system that is most appropriate for the given situation.

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