Volume of Solid w/ Semicircular Cross Sections in 1st Quadrant

Click For Summary

Homework Help Overview

The problem involves finding the volume of a solid with a base in the first quadrant, bounded by the x-axis, y-axis, and the line x + 2y = 8. The solid has semicircular cross sections perpendicular to the x-axis.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the setup of the problem and question the validity of their initial integral setup for calculating volume. There is confusion regarding the correct interpretation of the semicircular cross sections and their dimensions.

Discussion Status

Some participants have identified misunderstandings in their approaches, particularly regarding the radius of the semicircles. There is acknowledgment of differing interpretations of the cross section, and some have adjusted their reasoning based on feedback from others.

Contextual Notes

Participants reference an answer key that provides specific volume choices, indicating a potential discrepancy between their calculations and the expected results. There is an ongoing exploration of the correct method to arrive at the solution.

radtad
Messages
19
Reaction score
0
The base od a solid is a region in the 1st quadrant bounded by the x-axis, y-axis and the line x+2y=8. If cross sections of the solidperpendicular to the x-axis are semicircles, what is the volume of the solid?

How come the answer isn't just the intgegral from 0-8 of 1/2pi(4-x/2)^2
 
Physics news on Phys.org
radtad said:
The base od a solid is a region in the 1st quadrant bounded by the x-axis, y-axis and the line x+2y=8. If cross sections of the solidperpendicular to the x-axis are semicircles, what is the volume of the solid?

How come the answer isn't just the intgegral from 0-8 of 1/2pi(4-x/2)^2

That's what it looks like to me. Is it the wrong answer?
 
yea according to the answer key its wrong
 
choices are
a. 12.566 b. 14.661 c. 16.755 d 67.021 e 134.041

i keep ending up with choice d but the answer key says its choice c
 
Oh I see now. I misunderstood the problem. I did it by finding the solid after rotating about the x-axis and integrating... But the cross section of this solid is the circle whose diameter is from y=0 to y=4-x/2. We were thinking the cross section was a circle with diameter from y=-(4-x/2) to y=4-x/2. But if we make the radius (4-x/2)/2, then we get the right answer.

0-8 of 1/2pi[1/2(4-x/2)]^2 is correct.
 
yea i realized that too thanks
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
14K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
2
Views
1K