Question
A thin liquid film formed between a U-shaped wire and a light slider supports a weight of 1.5 x10–2N (see figure). The length of the slider is 30 cm and its weight negligible. The surface tension of the liquid film is
-
0.0125 Nm-1
-
0.1 Nm-1
-
0.05 Nm-1
-
0.025 Nm-1
Solution
D.
0.025 Nm-1
The force of surface tension acting on the slider balances the force due to the weight.
⇒F = 2Tl = w
⇒2T(0.3) = 1.5 x 10–2
⇒T = 2.5 x 10–2 N/m
