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A soap film is trapped between a frame and a wire of length 10 cm as shown. If the surface tension is given as 0.0049 N/m, what will be the value of m (in mg) such that the wire remains in equilibrium?

A soap film is trapped between a frame and a wire of length 10 cm as shown. If the surface tension is given as 0.0049 N/m, what will be the value of m (in mg) such that the wire remains in equilibrium? Correct Answer 100

For the wire to be in equilibrium, Force exerted by the film on the wire due to surface tension (acting upwards) must be equal to the downward force due to the weight of the wire (acting downwards). If σ=surface tension, l=length of the wire 2σl = mg Substituting all the values, m = 2σl/g = 2 * 0.0049 * 0.01 ⁄ 9.81 = 99.9mg.

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