trying to calculate the moment of inertia of a sphere. When I calculate moment of inertia by using dI of a small disk (dI=1/2dmy^2) I have a different answer with when I calculate it through expression I=integral(r^2dm). I have two different answers. Why integral method (the second picture) doesn't work ?

Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
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I'm trying to calculate the moment of inertia of a sphere. When I calculate moment of inertia by using dI of a small disk (dI=1/2dmy^2) I have a different answer with when I calculate it through expression I=integral(r^2dm). I have two different answers. Why integral method (the second picture) doesn't work ?

гоще
SOSI
8
als
–
LA
F
11
Год
годи
10 вищ 9
я
WZ
дон
ша
sb
=ZI =
[bg JЖZ=L30+ yoz - so I udZ - [t
ІШZ=I
S
І
st
нач
5F.07 - %,p ] uaz = &p(,27,2,02-no) Sutr =
с
= apIn&+2,07-no] од на
0-
=
근
= &p.ua_{2-b] 0;f = <I
ам((ави))) zh of =FI
b
трел S =I в
Л
домен - - d
Ш
z? -.g-h
루
ap (zhuld =wop
арди = пр'прЈ =шр
(
гр
t P
ab h
II
т
H
с
t
Z
отариа
III.
Transcribed Image Text:гоще SOSI 8 als – LA F 11 Год годи 10 вищ 9 я WZ дон ша sb =ZI = [bg JЖZ=L30+ yoz - so I udZ - [t ІШZ=I S І st нач 5F.07 - %,p ] uaz = &p(,27,2,02-no) Sutr = с = apIn&+2,07-no] од на 0- = 근 = &p.ua_{2-b] 0;f = <I ам((ави))) zh of =FI b трел S =I в Л домен - - d Ш z? -.g-h 루 ap (zhuld =wop арди = пр'прЈ =шр ( гр t P ab h II т H с t Z отариа III.
01
sol
8
에
8
니를
=
te
c
(1
40
bun
8 ㄱ
- ㅂㅂ
E-2 - 10.
=BIG
[50]]] = [ ²0 + 500
WPIN=I
eb h
so some
8
ше
[1]
W
д иш б
=
11
11
u-d
-
- 암을
-
루
327-29 - R
근
ep(200))) <By T = ² I
10
₂8 mp 7 = IP f
plchund=up
ep4 = sop'supd=up
J
= p (7272 2,07-10) S₩₩드=
no) °S HAT?
b
0-
= 2p [12+ c2207-10] ] 루
J
[tode22-20
J
팬
p
I 쿵 ㅇㅇ
201
n
2
내
근
도
근
Z
ep
↓
M
ㄱ
+
(2xouds)t •
ㅁㅇ
0
8
Transcribed Image Text:01 sol 8 에 8 니를 = te c (1 40 bun 8 ㄱ - ㅂㅂ E-2 - 10. =BIG [50]]] = [ ²0 + 500 WPIN=I eb h so some 8 ше [1] W д иш б = 11 11 u-d - - 암을 - 루 327-29 - R 근 ep(200))) <By T = ² I 10 ₂8 mp 7 = IP f plchund=up ep4 = sop'supd=up J = p (7272 2,07-10) S₩₩드= no) °S HAT? b 0- = 2p [12+ c2207-10] ] 루 J [tode22-20 J 팬 p I 쿵 ㅇㅇ 201 n 2 내 근 도 근 Z ep ↓ M ㄱ + (2xouds)t • ㅁㅇ 0 8
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but why we cant use formula I=integral(r^2dm) directly and get the same result? we can choose a small element dm=p(piy^2)dz and yet the answer is different. I cant understand the reason why 

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