a crane lifts a 75 kg mass at a height of 8m . calculate the gravitational potential energy gained by the mass (g= 10N)

What is the thinnest soap film (excluding the case of zero thickness) that appears black when illuminated with light with a wavelength of 480 ? the index of refraction of the film is 1.34, and there is air on both sides of the film. express your answer in nanometers. hint 1. how to approach th