Question

An aluminium sphere is dipped into water at 10°C. If the temperature is increased, the force of buoyancy
(a) will increase
(b) will decrease
(c) will remain constant
(d) may increase or decrease depending on the radius of the sphere

Answer 1

(b) will decrease

When an aluminium sphere is dipped in water and the temperature of water is increased, the aluminium will start expanding leading to increase in its volume. This will lead to increase in the surface area of the shell and it'll exert less pressure on the water such that the volume of the sphere submerged in water will decrease and it'll start float easily on water. Now, the volume of water displaced will be less compared to what was displaced initially. Therefore, the force of buoyancy will decrease, as it is directly proportional to the volume of water displaced.