Question:
Cylinders and Spheres...?
anonymous
2009-06-18 11:12:35 UTC
Sorry that i can't show you pictures but please try and picture them or you could draw a little sketch?

The radius of the base of a cylinder is 2x cm and the height of the cylinder is h cm.
The radiuse of a sphere is 3x cm.
The volume of the cylinder is equal to the voluse of the sphere.

Express h in terms of x, give your answer in its simplest form.

Please give answer and show working out!!!

Thanks, i will give points to the best answer! =]
Six answers:
Chris L
2009-06-18 11:25:15 UTC
Volume of a sphere = (4/3)πr³

Volume of a cylinder = hπr²



Since we know the radius of the cylinder is 2x cm, and the height is h cm, the cylinder's volume is:

V = hπ(2x)², or 4πhx²



Since we know the radius of the sphere is 3x cm, the sphere's volume is:

V = (4/3)(π)(3x)³, or 36πx³



Since the volumes are equal, write an equation and solve for "h":

4πhx² = 36πx³; divide both sides by 4πx²...

h = (36/4)(π/π)(x³/x²) = 9x
?
2016-12-24 19:00:59 UTC
Assuming the pyramid must be a familiar sq. pyramid, the biggest sq. pyramid interior a cube with area length d, could have top f = d and base area e = d (such that it shares a cube's area as its base), and its apex on the middle of the different cube area, such that its quantity V[pyramid] = (a million/3) e^2 f = d^3 / 3 = one-third the quantity V[cube] of the cube. subsequently, V[pyramid] is maximized as V[cube] is maximized. A cube interior a cylinder with radius b and top c, could have quantity V[cube] such that: V[cube] = min(2b, c)^3 *** Eq. a million on the grounds that c is inversely proportional Assuming the two caps of the cylinder are such that their around perimeters are parallel "small circles" of the sphere, (it extremely is, for the cylinders optimum radius b[max] = a million, c = 0; and additionally, for the cylinder's optimum top c[max] = 2, b = 0). enable element o be the middle of the sphere, and enable element p be on the edge of a around cap. enable oq be a radius of the cylinder such that pq is perpendicular to the around cap. Then, op = the around radius a = a million, pq = a million/2 the cylinder's top = c/2, and oq = the cylinder's radius b opq is a suitable triangle with hypotenuse op. via the Pythagorean Theorem, c^2 / 4 + b^2 = a million => c = 2 sqrt(a million - b^2) *** Eq. 2 on the grounds that 0 < b < a million and 0 < c < 2, we want in basic terms evaluate the beneficial branches of the sqrts. Now, b is inversely proportional to c, and the two are monotonic, because of the fact of this (via Eq. a million), V[cube] is maximized the place b = c. So our Pythagorean equation could be simplified to: b^2 / 4 + b^2 = a million => b = 2 sqrt(5) / 5 And, so V[pyramid, max] = V[cube, max] / 3 = b^3 / 3 = (2 sqrt(5) / 5)^3 / 3 = 8 sqrt(5) / seventy 5 *** answer ? 5.7% of the quantity of the sphere --- because of the fact the inradius of a unit cube is a million/2 and a circumradius is sqrt(3)/2, i could think of packing the sphere interior the cube could maximize area utilization. the main awkward quantity to fill seems to be the pyramid. So i could wager a maximal order could bypass like this (from innermost to outermost): pyramid, cylinder, cube, sphere i could wager that a minimum order could be cylinder, cube, sphere, pyramid
anonymous
2009-06-18 11:32:04 UTC
Vsp=volume of sphere = (4/3)*pi*R^3

R=radius of sphere



Vcy=volume of cylinder=pi*(r^2)*h

r=radius of cylinder



equate the two since the volumes are the same



(4/3)*pi*R^3=pi*(r^2)*h



substitute in the radii

R=3x

r=2x



this becomes

(4/3)*pi*(3x)^3=pi*((2x)^2)*h



now simplify and solve for h to get

h=9x
Zach
2009-06-18 11:24:31 UTC
I don't want to work your homework out for you, but I'll give you a hint:



volume sphere: 4/3*pi*r^3

volume cylinder: pi*r^2*h



to make the two volumes equivalent:

4/3*pi*r^3 = pi*r^2*h



Remove the terms that are similar from both sides and solve to find h=_______
Como
2009-06-18 11:32:13 UTC
V c = π r ² h = π ( 4 x ² ) h = 4 π x ² h



V s = (4/3) π r ^3 = (4/3) π (27) x ³ = 36 π x ³



4 π x ² h = 36 π x ³



x ² h = 9 x ³



h = 9 x
Henrik P
2009-06-18 11:25:35 UTC
Vcyl.=Pir^2h

Vsph.=4/3Pir^3

Pir^2h=4/3Pir^3

(2x)^2h=4/3(3x)^3

4x^2h=36x^3

h=36x^3/x^2

h=9x


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