Volume Shell Method: Setup & Evaluation

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The discussion focuses on using the shell method to calculate the volume of a solid generated by revolving the region defined by y = √x around the y-axis. The integral setup is V = 2∏∫(x)(√x)dx, with limits initially set from 0 to 8. A participant points out that the correct upper limit should be 9, leading to a recalculation of the volume. After adjusting the limits, the volume is found to be 972π/5. The importance of accurately determining the integration interval is emphasized in achieving the correct volume result.
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Homework Statement



Use the shell method to set up and evaluate the integral that gives the volume of the solid generated by revolving the plane region about the y-axis.
y = √x

Homework Equations



V=2∏∫p(x)h(x) dx
a=0
b=8

The Attempt at a Solution



V=2∏∫(x)(√x)dx
a=0 b=8
=2∏∫(x)3/2dx
=[(4∏/5)x5/2]8
V= when I do this my answer is wrong and too big
 

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chapsticks said:

Homework Statement



Use the shell method to set up and evaluate the integral that gives the volume of the solid generated by revolving the plane region about the y-axis.
y = √x

Homework Equations



V=2∏∫p(x)h(x) dx
a=0
b=8

The Attempt at a Solution



V=2∏∫(x)(√x)dx
a=0 b=8
=2∏∫(x)3/2dx
=[(4∏/5)x5/2]8
V= when I do this my answer is wrong and too big

It looks to me like the interval over which you should be integrating is [0, 9], not [0, 8]. Except for that, I don't seen anything wrong. I get an answer of 972\pi/5 for the volume.
 
Wow I should have paid close attention the graph is too small haha thank you.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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