Solving Volume of Solid S w/ Squares Perpendicular to y-Axis

  • Thread starter kplooksafterme
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In summary, the solid S is described as having a base bounded by the parabola y=5-2x^2 and the x-axis, with cross-sections perpendicular to the y-axis being squares. The volume V of this solid can be found by calculating the area of each square cross-section and adding them together.
  • #1
kplooksafterme
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Homework Statement


Consider the solid S described below.
The base of S is the region enclosed by the parabola y = 5 - 2x2 and the x-axis. Cross-sections perpendicular to the y-axis are squares.
Find the volume V of this solid.


Homework Equations





The Attempt at a Solution


I know how to answer these types of questions, but my question is what exactly does the question ask for? I can find the area bound by the parabola and the x-axis, but what does "cross-sections perpendicular to the y-axis are squares" mean?
thanks for any help
 
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  • #2
If the bounding functions were, for example, [itex]y=x+1[/itex], [itex]y=-x+1[/itex] and [tex]y=0[/itex] then the solid would be a square pyramid.

The object that's being described is something like a sqare 'bubble pyramid'.
 
  • #3
Imagine squares made of foam. at the base of the parabola, since y= 5- 2x2 has x-intercepts at [itex]\pm\sqrt{5/2}[/itex] your square have height as well as base of length [itex]2\sqrt{5/2}[/itex] (and so area 10). As y increases the corresponding x values decrease and so does the height of the square. Your solid is bounded by 4 curved sides. Of course, there is the base which is that parabola itself. There will also be two "edges" arcing from (-1, 0, [itex]-\sqrt{5/2}[/itex]) down to (0, 5, 0) and from (1, 0, [itex]\sqrt{5/2}[itex]) down to (0, 5, 0).
 

1. What is the formula for finding the volume of a solid with squares perpendicular to the y-axis?

The formula for finding the volume of a solid with squares perpendicular to the y-axis is V = ∫ab A(y) dy, where A(y) represents the area of the cross-section at a particular value of y and a and b are the limits of integration.

2. How do you determine the limits of integration for finding the volume?

The limits of integration are determined by the range of y-values where the solid exists. This can be determined by examining the given shape and identifying the minimum and maximum y-values of the squares perpendicular to the y-axis.

3. Can the volume of a solid with squares perpendicular to the y-axis be negative?

No, the volume cannot be negative as it represents a physical measurement. If the resulting volume calculation is negative, it is likely that the limits of integration were chosen incorrectly or the formula was applied incorrectly.

4. What is the difference between finding the volume with squares perpendicular to the y-axis and the x-axis?

The main difference is the orientation of the squares used to calculate the volume. When finding the volume with squares perpendicular to the y-axis, the squares are parallel to the y-axis and stacked along the x-axis. Whereas, when finding the volume with squares perpendicular to the x-axis, the squares are parallel to the x-axis and stacked along the y-axis.

5. Can the volume of a solid with squares perpendicular to the y-axis be calculated using a different integration method?

Yes, there are different methods of integration such as the disk method or the shell method that can also be used to find the volume of a solid with squares perpendicular to the y-axis. However, the formula V = ∫ab A(y) dy is specifically designed for this type of solid and is often the most efficient method to use.

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