问题25.从边缘21厘米的立方体木块的一个面切出一个半球形的凹陷,以使半球形表面的直径等于立方体表面的边缘。确定剩余块的体积和总表面积。
解决方案:
According to the question
Edge of the cubical wooden block (e) = 21 cm,
Diameter of the hemisphere = Edge of the cubical wooden block = 21 cm,
So, the radius of the hemisphere (r) = 10.5 cm
Now, we find the volume of the remaining block
V = volume of the cubical block – volume of the hemisphere
V = e3 − (2/3 πr3)
= 213 − (2/3 π10.53) = 6835.5 cm3
Now, we find the surface area of the block
AS = 6(e2) = 6(212)
Now, we find the curved surface area of the hemisphere
AC = 2πr2 = 2π10.52
The base area of the hemisphere is
AB = πr2 = π10.52
So, the remaining surface area of the box
= AS – (AC + AB)
= 6(212) – (2π10.52 + π10.52) = 2992.5 cm2
Hence, the remaining surface area of the block is 2992.5 cm2 and the volume is 6835.5 cm3
问题26:一个男孩正在玩一个玩具,该玩具是一个半球状的玩具,上面有一个与该半球相同的基本半径的右圆锥形。如果圆锥体底部的半径为21厘米,并且其体积为半球体积的2/3。计算圆锥体的高度和玩具的表面积。
解决方案:
According to the question
Radius of the cone (R) = 21 cm,
Radius of the hemisphere = Radius of the cone = r = 21 cm,
Now, we find the volume of the cone
V1 = 1/3 × πR2L
Here, L is the slant height of the comne
= 1/3 × π212L
Now, we find the volume of the Hemisphere
V2 = 2/3 × πR3
= 2/3 × π x 213 = 169714.286 cm3
Since, volume of the cone = 2/3 of the hemisphere,
So,
V1 = 2/3 V2
V1 = 2/3 ×169714.286
1/3 × π x 212 x L = 2/3×π x 213
L = 28 cm
So, the height of the cone is 28 cm
Now, we find the curved surface area of the cone
A1 = πRL
A1 = π × 21 × 28 cm2
Now, we find the curved curface area of the hemisphere
A2 = 2πR2
A2 = 2π(212) cm2
Hence, the total surface area of the toy
A = A1 + A2
= π × 21 × 28 + 2π(212)
= 5082 cm2
Hence, the curved surface area of the toy is 5082 cm2
问题27.考虑一个固体,它是一个悬在半球上的圆锥体形式。它们各自的半径为3.5厘米,固体的总高度为9.5厘米。查找固体的体积。
解决方案:
According to the question
Radius of the cone = Radius of the hemisphere = R = 3.5 cm,
Total height of the solid (H) = 9.5 cm,
Slant height of the cone = H – R
L = 9.5 – 3.5 = 6 cm
Now, we find the volume of the cone
V1 = 1/3 × πR2L
= 1/3 × π x 3.52 x 6 cm3
Now, we find the volume of the hemisphere
V2 = 2/3 × πR3
= 2/3 × π53 cm3 —————(ii)
Hence, the total volume of the solid is
V = V1 + V2
= 1/3 × π x 3.52 x 6 + 2/3 × π x 53
= 166.75 cm3
Hence, the volume of the solid is 166.75 cm3
问题28.木制玩具是通过从实心圆柱体的两端挖出半径相同的半球制成的。如果圆柱体的高度为10厘米,并且其底面的半径为3.5厘米,请找到玩具中木头的体积。
解决方案:
According to the question
Radius of the cylinder = Radius of the hemisphere (r) = 3.5 cm
Height of the hemisphere (h) = 10 cm
Now, we find the volume of the cylinder
V1 = π × r2 × h
= π × 3.52 × 10
Now, we find the volume of the hemisphere
V2 = 2/3 × πr3
= 2/3 × π x 3.53 cm3
Hence, the volume of the wood in the toy is
V = V1 – 2(V2)
= π × 3.52 × 10 – 2(2/3 × π x 3.53)
= 205.33 cm3
Hence, the volume of the wood in the toy is 205.33 cm3
问题29.尽可能大的球体是用7厘米边的木制实心立方体雕刻而成的。找到剩下的木头的体积。
解决方案:
According to the question
Diameter of the wooden solid = 7 cm,
Radius of the wooden solid = 3.5 cm,
Now, we find the volume of the cube
V1 = a3,
= 3.53
Now, we find the volume of sphere
V2 = 4/3 × π × r3
= 4/3 × π × 3.53
Hence, the volume of the wood left
V = V1 + V2
= 3.53 − 4/3 × π × 3.53
= 163.33 cm3
Hence, the volume of the wood left is 163.33 cm3
问题30.从一个高度为2.8 cm,直径为4.2 cm的实心圆柱体中挖出一个具有相同高度和直径的圆锥形腔。找到剩余固体的总表面积。
解决方案:
According to the question
Height of the cylinder = Height of the cone = H = 2.8 cm
Diameter of the cylinder = 4.2 cm,
So, the radius of the cylinder = Radius of the cone = R = 2.1 cm
Now, we find the curved surface area of the cylindrical part
A1 = 2πRH
= 2π(2.8)(2.1) cm2
Now, we find the curved surface area the cone = πRL
A2 = π × 2.1 × 2.8 cm2
The area of the cylindrical base = AB = πr2 = π(2.1)2
Hence, the total surface area of the remaining solid is
A = A1 + A2 + AB
= 2π(2.8)(2.1) + π × 2.1 × 2.8 + π(2.1)2
= 36.96 + 23.1 + 13.86
= 73.92 cm2
Hence, the total surface area of the remaining solid is 73.92 cm2
问题31.从侧面21厘米的实心立方体的一个面雕刻出最大的圆锥体。查找剩余固体的体积。
解决方案:
According to the question
Diameter of the cone = 21 cm,
So, the radius of the cone = 10.5 cm,
The height of the cone is equal to the side of the cone,
Now, we find the volume of the cube
V1 = e3
= 10.53
Now, we find the volume of the cone
V2 = 1/3 × πr2L
= 1/3 × π10.5221 cm3
Hence, the volume of the remaining solid
V = V1 – V2
= 10.53 – 1/3 × π x 10.52 x 21
= 6835.5 cm3
Hence, the volume of the remaining solid is 6835.5 cm3
问题32.实木玩具的形状是半球,上面覆盖着相同半径的圆锥体。半球的半径为3.5厘米,用于制造玩具的木材总量为166 5⁄6 cm 3 。找到玩具的高度。另外,请以Rs的比率找到玩具半球形部分的涂漆成本。每平方厘米10个。
解决方案:
According to the question
Radius of the hemisphere = 3.5 cm,
Volume of the solid wooden toy = cm3,
Hence, the volume of the solid wooden toy = volume of the cone + volume of the hemisphere
1/3 × πr2L + 2/3 × πr3 = 10016
1/3 × π3.52L + 2/3 × π3.53 = 10016
L + 7 = 13
L = 6 cm
Height of the solid wooden toy = Height of the cone + Radius of the hemisphere
= 6 + 3.5 = 9.5 cm
Now, we find the curved surface area of the hemisphere
A = 2πR2
= 2π(3.52) = 77 cm2
Cost of painting the hemispherical part of the toy = 10 x 77 = Rs. 770
Hence, the cost of painting the hemispherical part of the toy is 770 rupees
问题33.用一个长为55厘米,边长为4厘米的子弹的实心铅芯可以制造多少个球形子弹?
解决方案:
According to the question
Diameter of the bullet = 4 cm,
Radius of the spherical bullet = 2 cm
So, the volume of a spherical bullet is
V = 4/3 × π × r3
= 4/3 × π × 23
= 4/3 × 22/7 × 23 = 33.5238 cm3
Let’s assume that the total number of bullets be a.
So, the volume of ‘a’ number of the spherical bullets
V1 = V x a
= (33.5238 a) cm3
and the Volume of the solid cube = (55)3 = 166375 cm3
Now, we find the volume of ‘a’ number of the spherical bullets = Volume of the solid cube
33.5238 a = 166375
a = 4962.892
Hence, the total number of the spherical bullets is 4963
问题34.考虑一个儿童玩具,该玩具的顶部为圆锥形,半径为5厘米,安装在半球上,该半球是具有相同半径的玩具的底部。玩具的总高度为20厘米。找到玩具的总表面积。
解决方案:
According to the question
Radius of the conical portion of the toy (r) = 5 cm,
Total height of the toy (h) = 20 cm,
Length of the cone = L = 20 – 5 = 15 cm,
Now, we find the curved surface area of the cone
A1 = πrL
= π(5)(15) = 235.7142 cm2
Now, we find the curved surface area of the hemisphere
A2 = 2πr2
= 2π(5)2 = 157.1428 cm2
Therefore, The total surface area of the toy is
A = A1 + A2
= 235.7142 + 157.1428
= 392.857 cm2
Hence, the total surface area of the children’s toy is 392.857 cm2
问题35.一个男孩正在玩一个圆锥形的玩具,上面放着半球形的表面。考虑插入玩具的圆柱体。圆锥的直径与玩具的圆柱体和半球形部分的半径相同,为8厘米。圆柱体的高度为6厘米,玩具的圆锥形部分的高度为3厘米。假设将男孩的玩具插入圆柱体中的条件,然后找到插入玩具后空置的圆柱体的体积。
解决方案:
According to the question
Diameter of the cone = Diameter of the Cylinder = Diameter of the Hemisphere = 8 cm,
So, Radius of the cone = Radius of the cylinder = Radius of the Hemisphere = r = 4 cm
Height of the conical portion (L) = 3 cm,
Height of the cylinder (H) = 6 cm,
Now, we find the volume of the cylinder
V1 = π × r2 × H
= π × 42 × 6 = 301.7142 cm3
Now, we find the vcolume of the Conical part of the toy
V2 = 1/3 × πr2L
= 1/3 × π42 × 3 = 50.2857 cm3
Now, we find the volume of the hemispherical part of the toy
V3 = 2/3 × πr3
= 2/3 × π43 = 134.0952 cm3
Hence, the remaining volume the cylinder left vacant after insertion of the toy is
V = V1 – (V2 + V3)
= 301.7142 – (50.2857 + 134.0952) = 301.7142 – 184.3809
= 117.3333 cm3
Hence, the remaining volume the cylinder left vacant after insertion of the toy is 117.3333 cm3
问题36.考虑一个由高度为120厘米,半径为60厘米的直圆锥体构成的实体,直立于半径为60厘米的半球上,将其垂直放置在充满水的直圆柱体中,使其接触底部。如果圆柱体的半径为60厘米,高度为180厘米,则求出圆柱体内剩余的水量。
解决方案:
According to the question
Radius of the circular cone (r) = 60 cm,
Height of the circular cone (L) = 120 cm,
Radius of the hemisphere (r) = 60 cm,
Radius of the cylinder (R) = 60 cm,
Height of the cylinder (H) = 180 cm,
Now, we find the volume of the circular cone
V1 = 1/3 × πr2L
= 1/3 × π602 × 120
= 452571.429 cm3
Now, we find the volume of the hemisphere
V2 = 2/3 × πr3
= 2/3 × π603 = 452571.429 cm3
Now, we find the volume of the cylinder
V3 = π × R2 × H
= π × 602 × 180 = 2036571.43 cm3
Hence, the volume of water left in the cylinder is
V = V3 – (V1 + V2)
= 2036571.43 – (452571.429 + 452571.429)
= 2036571.43 – 905142.858 = 1131428.57 cm3
= 1.1314 m3
Hence, the volume of the water left in the cylinder is 1.1314 m3
问题37.考虑一个内径20厘米,高12厘米的圆柱形容器装满水。底部直径为8厘米,高度为7厘米的实心圆锥完全浸入水中。找到水的价值时
(i)从气缸中移出
(ii)留在气瓶中
解决方案:
According to the question
Internal diameter of the cylindrical vessel = 20 cm,
So, the radius of the cylindrical vessel (r) = 10 cm
Height of the cylindrical vessel (h) = 12 cm,
Base diameter of the solid cone = 8 cm,
So, the radius of the solid cone (R) = 4 cm
Height of the cone (L) = 7 cm,
(i) Now, we find the volume of water displaced out from the cylinder which is equal to the volume of the cone
V1 = 1/3 × πR2L
= 1/3 × π42 × 7 = 117.3333 cm3
Hence, the volume of the water displaced out of the cylinder is 117.3333 cm3
(ii) The volume of the cylindrical vessel is
V2 = π × r2 × h
= π × 102 × 12 = 3771.4286 cm3
Hence, the volume of the water left in the cylinder is
V = V2 – V1
= 3771.4286 – 117.3333 = 3654.0953 cm3
Hence, the volume of the water left in cylinder is 3654.0953 cm3