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Question 30918
JEE Physics · Hard

Fluid Mechanics: Buoyancy MCQ

Solve this quality-checked JEE multiple-choice question, then review the correct answer and explanation.

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BuoyancyHardQuestion 30918

Question

A balloon filled with helium rises because:
  1. A
    Helium is hot
  2. B
    Buoyant force of displaced air > weight of balloon + helium
    Correct
  3. C
    Helium repels gravity
  4. D
    Air pressure is lower at top

Correct answer

Buoyant force of displaced air > weight of balloon + helium

Explanation

Net upward force = Buoyant force − Total weight = (ρ_air − ρ_He)Vg (approximately). Since ρ_air > ρ_He, net upward force exists.

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