A rectangular plate of dimension `6 cm xx 4cm` and thickness `2mm` is placed with its largest face flat on the surface of water. Find the downward force on the plate due to surface tension. Surface tension of water is `7.0 xx 10^(-2)Nm^(-1)`.

Options

A. `1.8 xx 10^(-2)N`
B. `1.4 xx 10^(-2)N`
C. `2 xx 10^(-2) N`
D. `2.5 xx 10^(-2) N`

Answer

B

Explanation

Given, `l = 6 xx 10^(-2)m`,
`b = 4 xx 10^(-2)m`,
`d = 2 xx 10^(-3) m`,
and `S = 7.0 xx 10^(-2) Nm^(-1)`
Force on the plate due to surface tension is
`F = 2(l+b)S`
`= 2(6 xx 10^(-2) + 4 xx 10^(-2)) xx 7.0 xx 10^(-2)`
`= 1.4 xx 10^(-2) N`