small block with a mass of 0.150 kg is attached to a cord passing through a hole in a frictionless, horizontal surface. The block is originally revolving a distance of 0.5 m from thehole with a seed of 0.9 m/s. The cord is then pulled from below, shortening the radius of the circle in which the block revolves to 0.23 m. a) Explain if the tension force causes the change of angular momentum. b) What is the tension in the cord in the final situation when the block moving in a circle with smaller radius. c) How much work was done by the person who pulled on the cord

Antireflective coatings on solar cells are often made by applying a thin film of silicon nitride (sinx), which has an index of refractive of 1.2, on the top of the silicon solar cell, which has a refractive index of about 3.5. however, the sun emits radiation of various wavelengths which the solar cell absorbs, and the antireflective coating can only absolutely minimize the reflection of one of these wavelengths. the coating thickness is chosen to reduce the reflection of green/yellow light (e = 2.2 ev), which is the most intense color in the solar spectrum (shown below). which of the following coatings would minimize reflection of green/yellow light? the answer is 820 nm how? what is the angular width of the central maximum of an electron traveling at 2 x 108 m/s going through a single slit of width 1 mm.