A hollow spherical ball is made of an iron material of weight 5.25grm/m³. The ball has radius of 7 m and thickness of 200 cm. Find the weight of the ball?

4.75 kg

200 cm = 2 m

R = 7 m,  r = 7 - 2 = 5 m

Volume of ball = \(\frac{4}{3}\) \(\pi \)(R³ - r³)

                       =  \(\frac{4}{3}\) \(\pi \) ((7)³ - (5)³)

                       = \(\frac{4\;×\;22}{3\;×\;7}\) ×(218)

The weight of the spherical ball is = volume× 5.25g/m³

                                                      = \(\frac{4\;×\;22}{3\;×\;7}\) ×(218) × \(\frac{21}{4}\) = 4746 g or 4.75 kg