问题17.一个半径为6厘米的圆柱罐盛有油。每个半径为1.5厘米的铁球都浸入油中。需要多少个球体才能将油位提高两厘米?
解决方案:
Given that,
Radius of the cylinder jar = r1 = 6 cm,
Level to be rised = 2 cm,
Radius of each iron sphere = r2 = 1.5 cm,
Number of sphere = (Volume of Cylinder) / (Volume of Sphere)
= (π x (r1)^2 x h) / (4/3 x π x (r2)^3)
= ((r1)^2 x h) / (4/3 x (r2)^3) = (6 x 6×2) / (43 x 1.5 x 1.5 x 1.5)
Hence Number of Sphere is 16.
问题18:将一个内径为10 cm的量杯部分装满水。将四个直径分别为2厘米的球形球滴入其中,并将它们完全沉入水中。罐中水位会发生什么变化?
解决方案:
Given that,
Diameter of jar = 10 cm,
Radius of jar = 5 cm,
Diameter of the spherical bowl = 2 cm,
Radius of the ball = 1 cm.
Let the level of water be raised by h
Volume of jar = 4 x (Volume of spherical ball)
π x (r1)^2 x h = 4 x (4/3 x π x (r2)^3)
(r1)^2 x h = 4 x (4/3 x (r2)^3)
5 x 5 x h = 4 x 4/3 x 1 x 1 x 1
h = 16/75 cm
Hence Height of water in jar = 16/75 cm.
问题19.球体的直径为6厘米。将其熔化并拉成直径为0.2厘米的金属丝。找到电线的长度。
解决方案:
Given that,
Diameter of sphere = 6 cm,
Radius of sphere = d/2 = r1 = 6/2 = 3 cm,
Diameter of the wire = 0.2 cm,
Radius of the wire = r2 = 0.1 cm,
Volume of sphere = Volume of wire
4/3 x π x (r1)^3 = π(r2)^2 x h
4/3 x 3 x 3 x 3 = 0.1 x 0.1 x h
h = 3600 cm = 36m
Hence length of wire = 36 m.
问题20:中空球形壳的内表面和外表面的半径分别为3 cm和5 cm。如果熔化,则重新铸成高度为22/3 cm的实心圆柱体。找到圆柱体的直径。
解决方案:
Given that,
Internal radius of the sphere = r1 = 3 cm,
External radius of the sphere = r2 = 5 cm,
Height of the cylinder = h = 8/3cm,
Volume of the spherical shell = Volume of cylinder
4/3π(r23 – r13) = π x (r3)^2 x h
4/3(53 – 33) = 8/3 x (r3)^2
(r3)^2 = √49
r3 = 7 cm
Hence Diameter of the cylinder is 2 x radius = 14 cm.
问题21.半径为7 cm的导线半球被铸成高度为49 cm的右圆锥形。找到底座的半径。
解决方案:
Given that,
Radius of the hemisphere = Volume of cone
2/3 π(r1)^3 = 1/3 π(r2)^2 x h
2/3 x 7^3 = 1/3 x (r2)^2 x 49
(r2)^2 = (2x7x7x7x3) / (3×49)
(r2)^2 = 2058147
r2 = 3.47 cm
Hence radius of the base is 3.74 cm.
问题22.将一个内部半径和外部半径分别为2 cm和4 cm的空心球熔化成一个底部半径为4 cm的圆锥体。找到圆锥体的高度和倾斜高度。
解决方案:
Given that,
Hollow sphere external radius = r2 = 4 cm,
Internal radii = r1 = 2 cm,
Cone base radius (R) = 4 cm.
Height = h
Volume of cone = Volume of sphere (Given)
1/3 π(r)^2 x h = 4/3 x π x ((r2)^2 – (r1)^2)
4^2 x h = 4(43 – 23)
h = 14 cm
As we know that Slant Height = √(r)2 + (h)2
l = √(4)2 + (14)2 = √16 + 196 = √212 = 14.56 cm
Hence Height of cone is 14 cm and Slant Height is 14.56 cm.
问题23:将一个半径为10.5厘米的金属球熔化,然后重铸成小锥体,每个锥体的半径为3.5厘米,高度为3厘米。查找获得了多少个圆锥体。
解决方案:
Given that,
Metallic sphere of radius = 10.5 cm,
Cone radius = 3.5 cm,
Height of radius = 3 cm,
Let the number of cones obtained be x
Vs = X x Volume of cone
4/3 x π x (r)^3 = X x 1/3 π (r)^2 h
X = (4 x 10.5 x 10.5 x 10.5) / (3.5 x 3.5 x 3)
X = 126
Hence number of cones is 126.
问题24.一个圆锥和一个半球具有相等的底和相等的体积。找到他们的身高比例。
解决方案:
Given that,
A cone and a hemisphere have equal bases and volumes.
Volume of cone = Volume of hemisphere
1/3πr2h = 2/3πr3
r2h = 2r3
h = 2r
h x r = 2/1
h : r = 2:1
Therefore the ratio is 2 : 1
问题25.一个圆锥,一个半球和一个圆柱体站在相等的基础上,并且具有相同的高度。证明它们的体积比例为1:2:3。
解决方案:
Given that,
A cone, a hemisphere and a cylinder stand on one equal bases and have the same weight
hence,
Volume of cone : Volume of hemisphere : Volume of cylinder
1/3 πr2h : 2/3 πr3 : πr2h
Multiplying by 3
πr2h : 2πr3 : 3πr2h
πr3 : 2πr3 : 3πr3 (Given that r = h and r2h = r3)
Hence, the ratio is 1:2:3.
问题26.半径为12厘米的圆柱桶盛有20厘米深的水。将球形的球落入桶中,从而使水位上升6.75厘米。球的半径是多少?
解决方案:
Given that,
Radius of cylindrical tub = 12 cm,
Depth = 20 cm,
Let r be the radius of the ball then,
Volume of the ball = Volume of water raised
4/3 x π x (r)^3 = π x (r)^2 x h
r^3 = (3.14x(12)2 x 6.75 x 3) / 4
r^3 = 729
r = 9 cm
Hence radius of the ball is 9 cm.
问题27.最大的球体是从侧面10.5厘米的立方体中雕刻出来的。找到球体的体积。
解决方案:
Given that,
Side of cube = 10.5 cm,
Diameter of the largest sphere = 10.5 cm so r = 5.25 cm
Volume of sphere = 4/3πr3 = 4/3 × 22/7 × 5.25 × 5.25 × 5.25 = 606.375 cm3
Hence Volume of Sphere is 606.375 cm3.
问题28.球体,圆柱体和圆锥体的直径相同。圆柱体以及圆锥体的高度等于球体的直径。找到它们的体积比。
解决方案:
Let us assume that r be the common radius and,
Height of the cone = Height of the cylinder = 2r (Given)
Let’s assume that,
v1 = Volume of sphere = 4/3 πr3
v2 = Volume of cylinder = πr2h = πr2 × 2r
v3 = Volume of cone = 1/3πr2h = 1/3πr3
Now
v1 : v2 : v3 = 4/3πr3 : 2πr3 : 2/3πr3
= 4 : 6 : 2 = 2 : 3 : 1
Hence the ratio of their volumes is 2 : 3 : 1.
问题29.一个边长为4厘米的立方体包含一个接触其边的球体。找到之间的差距的体积。
解决方案:
Given that,
Cube side = 4cm
Volume of cube = (4 cm)3 = 64 cm3
Diameter of the sphere = Length of the side of the cube = 4 cm
Therefore radius of the sphere = 2cm
Volume of the sphere = 4/3πr3 = 4/3 × 22/7 × (2)3 = 33.52 cm3
Volume of gap = Volume of cube – Volume of sphere
= 64 – 33.52 = 30.48 cm3
Hence the volume of the gap in between is 30.48 cm3.
问题30.半球形水箱由1厘米厚的铁皮制成。如果内半径为1 m,则找到用于制造水箱的铁的体积。
解决方案:
Given that,
Inner radius of the hemispherical tank = 1 m = r1,
Thickness of the hemispherical tank = 1 cm = 0.01 m,
Outer radius of hemispherical tank = r2 = (1 + 0.01) = 1.01 m,
Volume of iron used to make the tank = 2/3 π x ((r2)3 – (r1)3)
= 2/3 x 22/7 x [(1.01)3 – (1)3]
= 0.06348 m^3
Hence volume of the iron used to make the tank is 0.06348 m3.
问题31.胶囊是直径3.5毫米的球形。填充此胶囊需要多少药(mm3)?
解决方案:
Given that,
Diameter of capsule = 3.5 mm
Radius = 3.5/2 = 1.75 mm
Volume of spherical sphere = 4/3πr3
= 4/3 × 22/7 × (1.75)3
= 22.458 mm3
Therefore 22.46 mm3 of medicine is required.
问题32.月亮的直径大约是地球直径的四分之一。地球上月球的体积是多少?
解决方案:
Given that,
Diameter of moon = 1/4th Diameter of earth.
Let us assume, diameter of earth is d, so radius = d/2
Then diameter of moon = d/4
Radius = d/8
Volume of moon = 4/3πr3 = 4/3π(d/8)3 = 4/3 x (1/512) x πd3
Volume of earth = 4/3πr3 = 4/3π(d/2)3 = 4/3 x (1/8) x πd3
(Volume of moon) / (Volume of earth) = 1/64
Hence the volume of the moon is 1/64 of volume of earth.