vindzul
Answered

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A hollow metal sphere has an external diameter of 12 cm and a thickness of 2 cm. (i) Given that the mass of 1 cm of the metal is 5.4 g, find the mass of the hollow sphere in kg. (ii) The hollow sphere is melted and recast to form a solid sphere. Find the radius of the solid sphere.​

Sagot :

reinhard10158

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

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