Volume of Rotated Function: Shell Method for y=1/x on [1,4]

  • Thread starter Thread starter physstudent1
  • Start date Start date
  • Tags Tags
    Method Shell
Click For Summary
SUMMARY

The discussion focuses on calculating the volume of the function y=1/x rotated about the x-axis over the interval [1,4] using the shell method. The solution involves expressing the volume as a sum of two integrals due to the varying radius and length of the shells in different regions. Specifically, the radius is defined as y, and the length of the shell varies between y=1/4 and y=1, where the length is dependent on y. The integration is performed using the formula 2π∫(1/y)y(dy) with appropriate limits of integration.

PREREQUISITES
  • Understanding of the shell method for volume calculation
  • Knowledge of integral calculus, specifically definite integrals
  • Familiarity with the function y=1/x and its graphical representation
  • Ability to manipulate equations to express variables in terms of others
NEXT STEPS
  • Study the shell method in detail, focusing on volume calculations
  • Learn how to sketch regions for functions and identify limits of integration
  • Explore the concept of variable radius and length in volume integrals
  • Practice solving similar problems involving rotation of functions about axes
USEFUL FOR

Students studying calculus, particularly those focusing on volume calculations using the shell method, as well as educators seeking to explain these concepts effectively.

physstudent1
Messages
267
Reaction score
1

Homework Statement


Find the volume of the function rotated about the x-axis over the given interval:

y=1/x

on interval [1,4]

for this specific problem it says to sketch the region and express as a sum of two integrals.

Homework Equations


The Attempt at a Solution



I'm not sure why you need to express it as a sum of two integrals. Since its about the x-axis I solved so that it was x=1/y for the radius and the height would then be y therefore with the shell method it would be 2*pi* \int (1/y)y(dy) the limits of integration being 1 to 4
 
Physics news on Phys.org
Shells means integrating 2*pi*r*l where r is the radius of the shell and l is the length of the shell. There are two regions of integration because between y=1/4 and y=1 the radius is y and the length depends on y (but it's not what you wrote). Between y=0 and y=1/4 the length of the shell is constant and equal to 3. If you sketched the region (and you should) I would suggest using that sketch.
 
Ohhhh, okay I get what your saying about the the 2 shells I see on the graph now as well, however I am confused about how to find what the radius is in terms of y I thought you just solved the original equation so that it was x= ??
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 13 ·
Replies
13
Views
2K
Replies
3
Views
2K
Replies
1
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K