Answer:
(i) 3.438159 kg
(ii) 5.336803297 cm
Step-by-step explanation:
the external diameter = 12 cm, => the radius = 6 cm.
the internal diameter = 12 - 2×2 = 8 cm, radius = 4 cm.
I assume the mass of 1 cm³ (not cm) is 5.4 g (very, very light metal).
the material is in the volume of external sphere minus internal (empty) sphere.
the volume of a sphere is
4/3 × pi×r³
V-e = 4/3 × pi×6³ = 4/3 × pi×216 = 4×pi×72 = 904.7786842 cm³
V-i = 4/3 × pi×4³ = 4/3 × pi×64 = 268.0825731 cm³
V-e - V-i = 4/3 × pi×(216-64) = 4/3 × pi×152 = 636.6961111 cm³
1cm³ = 5.4g
636.6961111 cm³ = 5.4×636.6961111 = 3438.159g = 3.438159 kg
for (ii) we need to work with the volume of the material and calculate backwards to find the radius of the sphere with the full volume of that size.
636.6961111 = 4/3 × pi×r³ = 4/3 × pi×152
152 = r³
r = 5.336803297
