Question

A uniform solid sphere of mass M and radius a is surrounded symmetrically by a uniform thin spherical shell of equal mass and radius 2a..Find the gravitational field at distance 5/2a from the centre..
okay 5/2a is outside both sphere and shell so I found E=GM/r^2=4GM/25 a^2
answer is 8GM/25a^2 in the end they have written resultant field E=2E'=8GM/25a^2 why?
which resultant ? :S

Answer 1

superposition principle .

Answer 2

total mass is 2M ... you can consider them as point masses .. since the point is outside .. their radius no longer matters!!

Answer 3

okay so what do they mean by resultant?
mass 2m isnt related to resultant or smto.O

Answer 4

"super position principle"

Answer 5

wo to SHM me hota hai :P

Answer 6

simple shell theorem!!.. ahh study basics first!! :XXX

Answer 7

arrre okay shell theorem but why have they written resultant ._.

Answer 8

not only in SHM, SPP finds its place in many theories.

Answer 9

you both are giving opposite answers

Answer 10

resultant means.. there are two masses.. so field due to both masses!!!

Answer 11

if its superposition principle then it should be
16GM^2/25a^2 something

Answer 12

yea yea superposition is the same thing.. you algebraicly add up the fields!!! due to each mass!!!

Answer 13

okay thanks :P "professor"

Answer 14

and how did you get 16?????

Answer 15

one 2 from @Mashy and one 2 from @shubhamsrg

Answer 16

:P

Answer 17

i got it now

Answer 18

\[E1 + E2 = 4GM/25a^{2}+4GM/25a^{2} = 8GM/25a^{2}\]

Answer 19

Because they are in same direction what if they are not?

Answer 20

why 2 from me and 2 from him??? we didnt ask you to superpose OUR answers!!!! lol

Answer 21

lol :D

Answer 22

then you subtract!!

Answer 23

i mean.. do vector addition!!..

Answer 24

relax

Answer 25

no relaxing you are writing IIT!!

Answer 26

cool :P

Answer 27

:|

Answer 28

and sorry.. fields are in the opposite direction!!

Answer 29

opposite?