Question

A soap film is created in a small wire frame as shown in the figure. The sliding wire of mass m is given a velocity u to the right and assume that u is small enough so that film does not break. Plane of the film is horizontal and surface tension is T, then time to region the original position of wire is equal to :

A. `(um)/(T l)`
B. `(T l)/(um)`
C. `(m u^(2))/(l T)`
D. It will never regain original position

Answer 1

Correct Answer - A
`a = (2Tl)/(m)`
`v = I + at rArr 0 = u - at`
`t = (u)/(a) = (um)/(2Tl)`
Total time `T = 2t = (um)/(Tl)`