Volume in cylindrical coordinates

In summary, the conversation discusses finding the volume using cylindrical coordinates for two given equations. The person attempted to convert the equations to cylindrical coordinates and set up the limits for the variables, but when evaluating the integral, they got a negative volume. They also question if they copied the problem correctly and ask for clarification on the x,y equation of the intersection of the two surfaces.
  • #1
physics&math
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Homework Statement



Find the volume using cylindrical coordinates bounded by:

x2+y2+z2=2 and

z = x2+y2

Homework Equations



Converting to cylindrical coordinates:
z = √2-r2 and

z = r2

The Attempt at a Solution



I figured z would go from r2 to √2-r2
r from 0 to √2
and θ from 0 to 2∏.
However, when I evaluate the integral I get a negative volume. (And no, I did not forget to multiply by an extra r)

I have no idea where I've gone wrong.
 
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  • #2
physics&math said:

Homework Statement



Find the volume using cylindrical coordinates bounded by:

x2+y2+z2=2 and

z = x2+y2

Homework Equations



Converting to cylindrical coordinates:
z = √2-r2 and

z = r2

The Attempt at a Solution



I figured z would go from r2 to √2-r2
r from 0 to √2
and θ from 0 to 2∏.
However, when I evaluate the integral I get a negative volume. (And no, I did not forget to multiply by an extra r)

I have no idea where I've gone wrong.

What is the x,y equation of the intersection of your two surfaces? Are you sure you copied the problem correctly?
 

Related to Volume in cylindrical coordinates

1. What is the formula for calculating volume in cylindrical coordinates?

The formula for calculating volume in cylindrical coordinates is V = πr2h, where r is the radius and h is the height of the cylinder.

2. How is the volume in cylindrical coordinates related to the volume in Cartesian coordinates?

The volume in cylindrical coordinates is equivalent to the volume in Cartesian coordinates, as both systems use the same units of measurement. However, the formula for calculating volume in cylindrical coordinates takes into account the shape of the cylinder, while the formula for calculating volume in Cartesian coordinates does not.

3. Can volume in cylindrical coordinates be negative?

No, volume cannot be negative in any coordinate system. Volume is a measure of the space occupied by an object and cannot have a negative value.

4. What happens to the volume in cylindrical coordinates if the radius and height are both doubled?

If both the radius and height are doubled, the volume in cylindrical coordinates will increase by a factor of 8. This is because the formula for volume in cylindrical coordinates is V = πr2h, so doubling both r and h results in a volume of 22 * 2 = 8 times the original volume.

5. Can volume in cylindrical coordinates be used to calculate the volume of any 3-dimensional shape?

No, volume in cylindrical coordinates can only be used to calculate the volume of objects that have a cylindrical shape, such as cylinders, cones, and spheres. For other shapes, different coordinate systems and formulas are needed to calculate volume.

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