Volume between cone and cylinder with a shift
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I am trying to solve the following problem:
Compute the volume of the solid bounded by the $ z = 3 sqrt{x^2 + y^2} $ , the plane $ z = 0 $ , and the cylinder $ x^2 +(y−1)^2 = 1 $ .
I know I need to use a triple integral, integrating over $ z, r, $ and $ theta $, but I am not sure how to account for the $ y $ shift. How do I do this?
multivariable-calculus
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add a comment |
$begingroup$
I am trying to solve the following problem:
Compute the volume of the solid bounded by the $ z = 3 sqrt{x^2 + y^2} $ , the plane $ z = 0 $ , and the cylinder $ x^2 +(y−1)^2 = 1 $ .
I know I need to use a triple integral, integrating over $ z, r, $ and $ theta $, but I am not sure how to account for the $ y $ shift. How do I do this?
multivariable-calculus
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Rewrite the circle equation in polar coordinates and simplify for $r$ as a function of $theta$.
$endgroup$
– David H
May 4 '14 at 3:05
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Hi David - that was my original approach, but I cannot figure out how to make it work since the cylinder is shifted, meaning I cannot simply use z = 3r.
$endgroup$
– user145277
May 4 '14 at 16:24
add a comment |
$begingroup$
I am trying to solve the following problem:
Compute the volume of the solid bounded by the $ z = 3 sqrt{x^2 + y^2} $ , the plane $ z = 0 $ , and the cylinder $ x^2 +(y−1)^2 = 1 $ .
I know I need to use a triple integral, integrating over $ z, r, $ and $ theta $, but I am not sure how to account for the $ y $ shift. How do I do this?
multivariable-calculus
$endgroup$
I am trying to solve the following problem:
Compute the volume of the solid bounded by the $ z = 3 sqrt{x^2 + y^2} $ , the plane $ z = 0 $ , and the cylinder $ x^2 +(y−1)^2 = 1 $ .
I know I need to use a triple integral, integrating over $ z, r, $ and $ theta $, but I am not sure how to account for the $ y $ shift. How do I do this?
multivariable-calculus
multivariable-calculus
edited May 4 '14 at 2:08
colormegone
9,71321542
9,71321542
asked May 4 '14 at 1:53
user145277user145277
133
133
$begingroup$
Rewrite the circle equation in polar coordinates and simplify for $r$ as a function of $theta$.
$endgroup$
– David H
May 4 '14 at 3:05
$begingroup$
Hi David - that was my original approach, but I cannot figure out how to make it work since the cylinder is shifted, meaning I cannot simply use z = 3r.
$endgroup$
– user145277
May 4 '14 at 16:24
add a comment |
$begingroup$
Rewrite the circle equation in polar coordinates and simplify for $r$ as a function of $theta$.
$endgroup$
– David H
May 4 '14 at 3:05
$begingroup$
Hi David - that was my original approach, but I cannot figure out how to make it work since the cylinder is shifted, meaning I cannot simply use z = 3r.
$endgroup$
– user145277
May 4 '14 at 16:24
$begingroup$
Rewrite the circle equation in polar coordinates and simplify for $r$ as a function of $theta$.
$endgroup$
– David H
May 4 '14 at 3:05
$begingroup$
Rewrite the circle equation in polar coordinates and simplify for $r$ as a function of $theta$.
$endgroup$
– David H
May 4 '14 at 3:05
$begingroup$
Hi David - that was my original approach, but I cannot figure out how to make it work since the cylinder is shifted, meaning I cannot simply use z = 3r.
$endgroup$
– user145277
May 4 '14 at 16:24
$begingroup$
Hi David - that was my original approach, but I cannot figure out how to make it work since the cylinder is shifted, meaning I cannot simply use z = 3r.
$endgroup$
– user145277
May 4 '14 at 16:24
add a comment |
2 Answers
2
active
oldest
votes
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The problem is to compute the volume of the region $R$ bounded by the three surfaces,
$$begin{cases}z=0,\z=3sqrt{x^2+y^2},\x^2+(y-1)^2=1.end{cases}$$
This is clearly a task best accomplished using cylindrical coordinates. In terms of cylindrical coordinates $(x,y,z)=(rhocos{phi},rhosin{phi},z)$, the three surface equations become
$$begin{cases}z=0,\z=3sqrt{(rhocos{phi})^2+(rhosin{phi})^2},\(rhocos{phi})^2+(rhosin{phi}-1)^2=1,end{cases}$$
or
$$begin{cases}z=0,\z=3rho,~~~0leqrho\rho=2sin{phi},~~~0leqphi<pi.end{cases}$$
Thus, the volume of $R$ can be found by evaluating the following triple integral:
$$V=iiint_{R}dV\
=int_{0}^{pi}dphiint_{0}^{2sin{phi}}drho,rhoint_{0}^{3rho}dz\
=int_{0}^{pi}dphiint_{0}^{2sin{phi}}drho,(3rho^2)\
=int_{0}^{pi}dphi,(2sin{phi})^3\
=frac{32}{3}.$$
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The answer seems to be not right. It should be $32/3/sqrt 3$.
$endgroup$
– duanduan
Jan 7 '17 at 7:41
add a comment |
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HINT
Convert to cylindrical/polar coordinates
$$ z=3 ,r; z = 6 sin theta; , r = 2 sin theta, $$
the cylinder generator goes through $z$ axis. The volume computation is simpler than Viviani ( cylinder and sphere intersection).
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add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
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active
oldest
votes
$begingroup$
The problem is to compute the volume of the region $R$ bounded by the three surfaces,
$$begin{cases}z=0,\z=3sqrt{x^2+y^2},\x^2+(y-1)^2=1.end{cases}$$
This is clearly a task best accomplished using cylindrical coordinates. In terms of cylindrical coordinates $(x,y,z)=(rhocos{phi},rhosin{phi},z)$, the three surface equations become
$$begin{cases}z=0,\z=3sqrt{(rhocos{phi})^2+(rhosin{phi})^2},\(rhocos{phi})^2+(rhosin{phi}-1)^2=1,end{cases}$$
or
$$begin{cases}z=0,\z=3rho,~~~0leqrho\rho=2sin{phi},~~~0leqphi<pi.end{cases}$$
Thus, the volume of $R$ can be found by evaluating the following triple integral:
$$V=iiint_{R}dV\
=int_{0}^{pi}dphiint_{0}^{2sin{phi}}drho,rhoint_{0}^{3rho}dz\
=int_{0}^{pi}dphiint_{0}^{2sin{phi}}drho,(3rho^2)\
=int_{0}^{pi}dphi,(2sin{phi})^3\
=frac{32}{3}.$$
$endgroup$
$begingroup$
The answer seems to be not right. It should be $32/3/sqrt 3$.
$endgroup$
– duanduan
Jan 7 '17 at 7:41
add a comment |
$begingroup$
The problem is to compute the volume of the region $R$ bounded by the three surfaces,
$$begin{cases}z=0,\z=3sqrt{x^2+y^2},\x^2+(y-1)^2=1.end{cases}$$
This is clearly a task best accomplished using cylindrical coordinates. In terms of cylindrical coordinates $(x,y,z)=(rhocos{phi},rhosin{phi},z)$, the three surface equations become
$$begin{cases}z=0,\z=3sqrt{(rhocos{phi})^2+(rhosin{phi})^2},\(rhocos{phi})^2+(rhosin{phi}-1)^2=1,end{cases}$$
or
$$begin{cases}z=0,\z=3rho,~~~0leqrho\rho=2sin{phi},~~~0leqphi<pi.end{cases}$$
Thus, the volume of $R$ can be found by evaluating the following triple integral:
$$V=iiint_{R}dV\
=int_{0}^{pi}dphiint_{0}^{2sin{phi}}drho,rhoint_{0}^{3rho}dz\
=int_{0}^{pi}dphiint_{0}^{2sin{phi}}drho,(3rho^2)\
=int_{0}^{pi}dphi,(2sin{phi})^3\
=frac{32}{3}.$$
$endgroup$
$begingroup$
The answer seems to be not right. It should be $32/3/sqrt 3$.
$endgroup$
– duanduan
Jan 7 '17 at 7:41
add a comment |
$begingroup$
The problem is to compute the volume of the region $R$ bounded by the three surfaces,
$$begin{cases}z=0,\z=3sqrt{x^2+y^2},\x^2+(y-1)^2=1.end{cases}$$
This is clearly a task best accomplished using cylindrical coordinates. In terms of cylindrical coordinates $(x,y,z)=(rhocos{phi},rhosin{phi},z)$, the three surface equations become
$$begin{cases}z=0,\z=3sqrt{(rhocos{phi})^2+(rhosin{phi})^2},\(rhocos{phi})^2+(rhosin{phi}-1)^2=1,end{cases}$$
or
$$begin{cases}z=0,\z=3rho,~~~0leqrho\rho=2sin{phi},~~~0leqphi<pi.end{cases}$$
Thus, the volume of $R$ can be found by evaluating the following triple integral:
$$V=iiint_{R}dV\
=int_{0}^{pi}dphiint_{0}^{2sin{phi}}drho,rhoint_{0}^{3rho}dz\
=int_{0}^{pi}dphiint_{0}^{2sin{phi}}drho,(3rho^2)\
=int_{0}^{pi}dphi,(2sin{phi})^3\
=frac{32}{3}.$$
$endgroup$
The problem is to compute the volume of the region $R$ bounded by the three surfaces,
$$begin{cases}z=0,\z=3sqrt{x^2+y^2},\x^2+(y-1)^2=1.end{cases}$$
This is clearly a task best accomplished using cylindrical coordinates. In terms of cylindrical coordinates $(x,y,z)=(rhocos{phi},rhosin{phi},z)$, the three surface equations become
$$begin{cases}z=0,\z=3sqrt{(rhocos{phi})^2+(rhosin{phi})^2},\(rhocos{phi})^2+(rhosin{phi}-1)^2=1,end{cases}$$
or
$$begin{cases}z=0,\z=3rho,~~~0leqrho\rho=2sin{phi},~~~0leqphi<pi.end{cases}$$
Thus, the volume of $R$ can be found by evaluating the following triple integral:
$$V=iiint_{R}dV\
=int_{0}^{pi}dphiint_{0}^{2sin{phi}}drho,rhoint_{0}^{3rho}dz\
=int_{0}^{pi}dphiint_{0}^{2sin{phi}}drho,(3rho^2)\
=int_{0}^{pi}dphi,(2sin{phi})^3\
=frac{32}{3}.$$
answered May 8 '14 at 0:46
David HDavid H
21.7k24693
21.7k24693
$begingroup$
The answer seems to be not right. It should be $32/3/sqrt 3$.
$endgroup$
– duanduan
Jan 7 '17 at 7:41
add a comment |
$begingroup$
The answer seems to be not right. It should be $32/3/sqrt 3$.
$endgroup$
– duanduan
Jan 7 '17 at 7:41
$begingroup$
The answer seems to be not right. It should be $32/3/sqrt 3$.
$endgroup$
– duanduan
Jan 7 '17 at 7:41
$begingroup$
The answer seems to be not right. It should be $32/3/sqrt 3$.
$endgroup$
– duanduan
Jan 7 '17 at 7:41
add a comment |
$begingroup$
HINT
Convert to cylindrical/polar coordinates
$$ z=3 ,r; z = 6 sin theta; , r = 2 sin theta, $$
the cylinder generator goes through $z$ axis. The volume computation is simpler than Viviani ( cylinder and sphere intersection).
$endgroup$
add a comment |
$begingroup$
HINT
Convert to cylindrical/polar coordinates
$$ z=3 ,r; z = 6 sin theta; , r = 2 sin theta, $$
the cylinder generator goes through $z$ axis. The volume computation is simpler than Viviani ( cylinder and sphere intersection).
$endgroup$
add a comment |
$begingroup$
HINT
Convert to cylindrical/polar coordinates
$$ z=3 ,r; z = 6 sin theta; , r = 2 sin theta, $$
the cylinder generator goes through $z$ axis. The volume computation is simpler than Viviani ( cylinder and sphere intersection).
$endgroup$
HINT
Convert to cylindrical/polar coordinates
$$ z=3 ,r; z = 6 sin theta; , r = 2 sin theta, $$
the cylinder generator goes through $z$ axis. The volume computation is simpler than Viviani ( cylinder and sphere intersection).
edited Jan 8 '18 at 19:43
answered Jan 8 '18 at 19:18
NarasimhamNarasimham
21.2k62258
21.2k62258
add a comment |
add a comment |
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$begingroup$
Rewrite the circle equation in polar coordinates and simplify for $r$ as a function of $theta$.
$endgroup$
– David H
May 4 '14 at 3:05
$begingroup$
Hi David - that was my original approach, but I cannot figure out how to make it work since the cylinder is shifted, meaning I cannot simply use z = 3r.
$endgroup$
– user145277
May 4 '14 at 16:24