A solid body of volume 1000 cm³ and density 600 kg/m³ is completely immersed in water and tied to the bottom of the vessel by a light string. Taking g = 10 m/s², the string tension is N N. Find N.
Physics · Fluid Mechanics · pascal law and buoyant force
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Question

A solid body of volume 1000 cm³ and density 600 kg/m³ is completely immersed in water and tied to the bottom of the vessel by a light string. Taking g = 10 m/s², the string tension is N N. Find N.

G1 Physics · Accepted Answer

Body volume: V = 1000 cm³ = 1.0×10⁻³ m³. Buoyant force: B = ρ(water)Vg = 1000×10⁻³×10 = 10 N. Mass of the body: m = ρ(body)V = 600×10⁻³ = 0.6 kg. Therefore its weight is W = 0.6×10 = 6 N. Because the body tends to rise, the string pulls downward. For equilibrium, B = W+T. Hence, T = B−W = 10−6 = 4 N. Therefore, N = 4.