Question

A block of iron is kept at the bottom of a bucket full of water at $2^{\circ }\text{C}$. The water exerts buoyant force on the block. If the temperature of water is increased by $1^{\circ }\text{C}$, the temperature of the iron block also increases by $1^{\circ }\text{C}$. The buoyant force on the block by water

• A. will increase
• B. will decrease
• C. will not change
• D. may decrease or increase depending on the values of their coefficients of expansion.

Answer 1

The correct option is A will increase

Increasing the temperature of water from $2^{\circ }\text{C}$ to $3^{\circ }\text{C}$ increases the density of water [since density of liquid water is maximum at $4^{\circ }\text{C}$] and increases the volume of iron [due to thermal expansion].

Hence, buoyant force which is the product of the volume of the iron block and the density of water also increases.