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Largest coin or wire that floats on water by surface tension

This type of question, asked 4 times: May 2022 S1, 19 Apr 2026 S2, 13 May 2026 S2, 19 May 2026 S1. All 4 questions below, oldest first.

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  1. Question 1

    May 2022 S1

    36
    A steel coin of thickness dd and density ρ\rho is floating on water of surface tension TT. The radius of the coin (RR) is [gg = acceleration due to gravity]

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  2. Question 2

    19 Apr 2026 S2

    109
    A metal wire of length 'L' and density 'd' floats horizontally on the free surface of water. The maximum radius of the wire does not sink in water is [ TT = surface tension of water , gg = gravitational acceleration]

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  3. Question 3

    13 May 2026 S2

    112
    What is the radius of the biggest aluminium coin of thickness tt and density ρ\rho, which will be able to float on the water surface of surface tension TT? (gg = acceleration due to gravity)

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  4. Question 4

    19 May 2026 S1

    110
    A metal wire of length 'LL' and density 'dd' rests horizontally on the free surface of water. The maximum radius of the wire so that the wire does not sink in water is [TT = surface tension of water, gg = gravitational acceleration]

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