Asmall sphere is hung by a string from the ceiling of a van. when the van is stationary, the sphere hangs vertically. however, when the van accelerates, the sphere swings backward so that the string makes an angle of
θ
with respect to the vertical.
(a) derive an expression for the magnitude a of the acceleration of the van in terms of the angle
θ
and the magnitude g of the acceleration due to gravity.
(b) find the acceleration of the van when
θ=10.0∘
(c) what is the angle
θ
when the van moves with a constant velocity?

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.