The length of needle floating on the surface of water is 1.5 cm. Then addition to its weight required to lift the needle from water surface will be (surface tension of water = 7.5 N/cm):

22.5 N

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2.25 N

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0.25 N

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225N

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Solution

The correct option is A 22.5 N
Additional force required to lift the needle = force due to surface tension
Force along one side = $S u r f a c e t e n s i o n (S) \times L e n g t h (L)$
Net force = $2 (S \times L)$
$\Rightarrow F = 2 (7.5 N / c m \times 1.5 c m) = (11.25 N)$
$\Rightarrow F = 22.5 N ⟶ (A N S W E R)$

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