The surface tension of water in air is approximately 0.0756 N-m. If theatmospheric pressure is 101 kPa (abs), what is the pressure inside a droplet 0.254mmin diameter? (A) 99.83 kPa (abs) (B) 101.0 kPa (abs) (C) 101.5 kPa (abs) (D) 102.2 kPa (abs)

D

Explanation:

For a droplet which has only one surface.

P1 - P2 = 2T/r

Where

P1 and P2 are inside pressure? and outside pressure = 101kpa abs.

T - Surface tension = 0.0756N/m

r - droplet radius = 0.254mm/2 = 0.127mm = 0.000127m

P1 = (2 x 0.0756/0.000127) + 101000 = 102.19kpa

Therefore the inside pressure P1 = 102.2kpa abs