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GATE 2025 ME – Question 15

Fluid Mechanics · Fluid properties, fluid statics, forces on submerged bodies, stability of floating bodies · 1 mark · Multiple choice

Let a spherical block of ice at $-7$ °C be exposed to atmospheric air at 30 °C with the gravitational direction as shown in the figure below. What will be the overall direction of air flow in this situation?

A sphere labelled "Ice block, -7 °C" surrounded by air at 30 °C. Gravity points downward, and the directions upward, downward and sideward are marked.
  1. Upward
  2. Downward
  3. NO motion
  4. Sideward

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Show answer and explanation

Correct answer: (B) Downward

Explanation

The air next to the cold ice cools down and becomes denser, so it sinks. The overall flow around the ice is therefore downward, as in natural convection around a cold body.