The force required to take away a flat circular plate of radius 2 cm from the surface of water is [ Surface tension of water = 70 × 10⁻³ N m⁻¹, π = 22/7] (a) 4.4 × 10⁻⁴ N (b) 8.8 × 10⁻³ N (c) 6.6 × 10⁻⁴ N (d) 11 × 10⁻³ N

Answer: (b). Surface tension acts along the rim of the plate: F = T × 2π r. F = 70×10⁻³ × 2 × 22/7 × 0.02. F = 8.8 × 10⁻³ N. So the answer is (b).

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Q14MHT CET 2021 · 20 SEP · SHIFT 1Easy

Force due to Surface Tension

The force required to take away a flat circular plate of radius $2\text{ cm}$ from the surface of water is $[$ Surface tension of water $= 70 \times 10^{-3}\text{ N m}^{-1}, \pi = \frac{22}{7}]$

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Answer: (b)

Surface tension acts along the rim of the plate: $F = T \times 2\pi r$ .
$F = 70\times10^{-3} \times 2 \times \frac{22}{7} \times 0.02$ .
$F = 8.8 \times 10^{-3}\text{ N}$ . So the answer is (b).

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