The length of a needle floating on the surfac | vedclass

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(A) When a needle is floating on the surface of water,the surface tension acts along the length of the needle on both sides.The total length of contac

Vedclass · Accepted Answer

$22.5$

Vedclass · Answer

(A) When a needle is floating on the surface of water,the surface tension acts along the length of the needle on both sides.The total length of contact is $L_{total} = 2 	imes L = 2 	imes 1.5\,cm = 3.0\,cm$.The force required to lift the needle,in addition to its weight,is given by the formula $F = T 	imes L_{total}$,where $T$ is the surface tension.Given $T = 7.5\,N/cm$ and $L_{total} = 3.0\,cm$.$F = 7.5\,N/cm 	imes 3.0\,cm = 22.5\,N$.

The length of a needle floating on the surface of water is $1.5\,cm$. The force in addition to its weight required to lift the needle from the water surface will be...... $N$ (surface tension of water $= 7.5\,N/cm$).

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