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MHT CET202122 Sep 2021Evening ShiftPhysicsMechanical Properties of FluidsActual

A needle is 7 ~cm long. Assuming that the needle is not wetted by water, what is the weight of the needle, so that floats on water? [ T = surface tension of water =70 dyne cm ] [acceleration due to gravity =980 ~cm ~s ⁻² ]

Options

  1. A1 g wt
  2. B5 g wt
  3. C3 g wt
  4. D7 g wt

Correct answer

A. 1 g wt

Step-by-step solution

The weight of the needle is balanced by the force due to surface tension aligned & W =2 TL & =2 70 7 & =980 dyne & =1 ~g wt aligned

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