A rectangular film of liquid is extended from to . If the work done is , the value of the surface tension of the liquid is [2016]

STUDY MATERIALS
COURSES
MORE
SUCCESS STORY
ADMISSION
STORE

Back

JEE ADVANCE

CLASS XI - XII
CRASH COURSE

CLASS XI - XII

CRASH COURSE

JEE MAIN

CLASS XI - XII
CRASH COURSE

CLASS XI - XII

CRASH COURSE

NEET

CLASS XI - XII
CRASH COURSE

CLASS XI - XII

CRASH COURSE

BITSAT

CLASS XI - XII

CLASS XI - XII

CBSE BOARD

CLASS IX

CLASS X

CLASS XI

CLASS XII

CLASS VI

CLASS VII

CLASS VIII

UP BOARD

CLASS IX
CLASS X
CLASS XI
CLASS XII

CLASS IX

CLASS X

CLASS XI

CLASS XII

CUET

CRASH COURSE

CRASH COURSE

Courses

CLASSROOM COURSES
ONLINE COURSES

ONLINE COURSES

More

Solution

Q.
A rectangular film of liquid is extended from $(4 cm \times 2 cm)$ to $(5 cm \times 4 cm)$ . If the work done is $3 \times 10^{- 4}$ $J$ , the value of the surface tension of the liquid is [2016]

1 0.250 N $m^{- 1}$

2 0.125 N $m^{- 1}$

3 0.2 N $m^{- 1}$

4 8.0 N $m^{- 1}$

Ans.
(2)

Work done = Surface tension of film $\times$ Change in area of the film

or,    $W = T \times Δ A$

Here, $A_{1} = 4 cm \times 2 cm = 8 {cm}^{2}, A_{2} = 5 cm \times 4 cm = 20 {cm}^{2}$

   $Δ A = 2 (A_{2} - A_{1}) = 24 {cm}^{2} = 24 \times 10^{- 4} m^{2}$

   $W = 3 \times 10^{- 4} J, T = ?$

$∴$ $T = \frac{W}{Δ A} = \frac{3 \times 10^{- 4}}{24 \times 10^{- 4}} = \frac{1}{8} = 0.125$ $N$ $m^{- 1}$

Want Us to Email you About Special Offers & Updates?