The force required to take away a flat circular plate of radius 5 cm on the surface of water, will be: (surface tension of water =75× 10-3N/m )

Question

The force required to take away a flat circular plate of radius 5 cm on the surface of water, will be: (surface tension of water =75× 10-3N/m ) (A) 3.5 N (B) 7.5 π × 10-3N  (C) 15 π × 10-3N  (D) none of these

Tardigrade Admin · Accepted Answer

Using the relation, F=TL=T× 2π R Here, R=5cm=5× 10-2m T=75× 10-3N/m or F=75× 10-3× 2× π × 5× 10-2 So, F=7.5π × 10-3N

Q. The force required to take away a flat circular plate of radius $5 c m$ on the surface of water, will be : (surface tension of water $= 75 \times 10^{- 3} N / m$ )

$3.5 N$

$7.5 π$ $\times 10^{- 3} N$

$15 π$ $\times 10^{- 3} N$

none of these

Using the relation, $F = T L = T \times 2 π R$
Here, $R = 5 c m = 5 \times 10^{- 2} m$
$T = 75 \times 10^{- 3} N / m$ or
$F = 75 \times 10^{- 3} \times 2 \times π \times 5 \times 10^{- 2}$
So, $F = 7.5 π \times 10^{- 3} N$

Q. The force required to take away a flat circular plate of radius 5cm on the surface of water, will be : (surface tension of water =75×10−3N/m )

3.5N

7.5π ×10−3N

15π ×10−3N