A hollow spherical ball is made of an iron material of weight 10g/m³. The ball has external radius of 7 m and thickness of 15 cm. Find the weight of the ball?

904.3 g

15 cm = 0.15m

R = 7m , r = 7 - 0.15 = 6.85 m

Now,

Weight of ball = volume × g/m³

volume = \(\frac{4}{3}\) \(\pi \)(R³ - r³)

            = \(\frac{4}{3}\) × \(\frac{22}{7}\) (7³ - (6.85)³)

            = \(\frac{4}{3}\) × \(\frac{22}{7}\) × 21.58

            = 90.43 m³

Therefore, weight = 90.43 × 10 = 904.3 g