a) Define the term surface tension
(b) Calculate the force required to lift a needle 4cm long off the surface of water if the surface tension of water is 7.3 x 10\(^{-4}\) NM\(^{-1}\)
Verified Correct Answer: .
Physical Principles & Numerical Solution
a) Surface tension is defined as a force per unit length perpendicular to any line on the surface of the liquid OR Property of a liquid which makes the surface of liquid behave like an elastic skin.
(b) Surface tension =\(\frac{F}{2L}\)
F = 7.3 x 1\(^{-2}\) x 2 x 0.04 = 5.8 x 10\(^{-3}\)N
Source: Myschool Past Questions Archive (Record #54136)