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?
Answer & explanation
Correct answer: option 3
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