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Mechanical Properties Of Fluids

Question
CBSEENPH11026286

The work done in increasing the size of a soap film for 10cm × 6cm  to 10cm × 11cm is 3  × 10-4 J. The surface tension of the film is

  • 1.0  × 10-2 N/m

  • 6.0  × 10-2 N/m

  • 3.0  × 10-2 N/m

  • 1.5  × 10-2 N/m

Solution

C.

3.0  × 10-2 N/m

Given:-

Increasing size ΔA = (10 × 10-2 × 11 × 10-2 - 10 × 10-2 × 6 × 10-2 )

                        ΔA = ( 10 × 11 - 10 × 6 ) 

Work done = area increased  × surface tension

      surface tension 

              ST3 × 10-42 × 10 × 11 - 10 × 6  × 10-4          

(since soap film has two surfaces)

               ST = 3 × 10-2 N/m