Question

A rubber ball floats on water with it’s 1/3rd volume outside water. What is the density of rubber ?

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Answer

V = total volume of rubber ball

ρ = density of the rubber ball

1/3rd of V is outside water

Therefore, volume inside water V – 1\over3V = 2\over3V

By the principle of flotation,

Weight of ball = Weight of water displaced by the immersed part of the ball.

and density of water = 1000 kg m-3

i.e., V × ρ × g = 2\over3V × 1000 × g

Hence, ρ = 2000/3 = 667 kg m-3

Hence,

Density of rubber = 667 kg m-3

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