Page 5 - Lesson Note-4-Ch-13 SA and Volume(Sphere)

Example-6
A shot-putt is a metallic sphere of radius 4.9 cm. If the density of the metal is 7.8
gm per , find the mass of the shot-putt.
3
Solution: Radius = 4.9 cm
Volume of sphere
4
=  r 3
3
4 22


=   4.9 4.9 4.9cm
3
3 7
= 493cm 3 (nearly )

3
Mass of 1 cm = 7.8 gm
So, mass of shot-putt = (7.8 × 493) gm
= 3845.44gm = 3.85 g(nearly).

Example-7

Find the volume of a hollow spherical shell whose external and internal diameters
are 10 cm and 6 cm respectively.
Solution
6
Given , R = 10 = 5 cm r = = 3 cm
2 2
Volume of hollow spherical shell
4
=  ( R − 3 r 3 )
3
4 22 3
3
=   ( 5 − 3 )
3 7
4 22
=   (125 27− )
3 7
4 22
=   98
3 7
= 410.66cm 3

5