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})
Explanation
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 = F/21
=7.3 x 1(^{-2}) x 2 x 0.04 = 5.8 x 10(^{-3})N