Question

An aluminium sphere is dipped into water. Which of the following is true?

• A. Buoyancy will be less in water at 0°C than that in water at 4°C.
• B. Buoyancy will be more in water at 0°C than that in water at 4°C.
• C. Buoyancy in water at 0°C will be same as that in water at 4°C.
• D. Buoyancy may be more or less in water at 4°C depending on the radius of the sphere.

Answer 1

Answer: (A)

Buoyancy will be less in water at 0°C than that in water at 4°C.

Answer 2

As buoyancy at $0{^\circ}C,F_{b} = V\rho_{0}g$ and buoyancy at $4{^\circ}C,F`_{b} = V\rho_{4}g$

$\frac{F_{b}}{F_{b}} = \frac{\rho_{0}}{\rho_{4}} < 1$ (density of water at $4{^\circ}C$is maximum)

i.e., $F_{b} < F`_{b}$