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A solid sphere of radius 4cm has a mass of 64kg. What wil...

A solid sphere of radius 4cm has a mass of 64kg. What will be the mass of a shell of the same metal whose internal and external radii are 2cm and 3cm respectively?

A.

5kg

B.

16kg

C.

19kg

D.

6kg

Correct answer is A

13(12)2

= 43

= 33

= 433

m = 64kg, V = 4πr33

= 4π(4)33

= 256π3 x 10-6m3

density(P) = MassVolume

= 64256π3×106

= 64×3×106256

= 34×106

m = PV = 34π×106 x 43 π[32 - 22] x 10-6

34×106 x 43 x 5 x 10-6

= 5kg