Very far from earth (at r=[infinity]), a spacecraft has run out of fuel and its kinetic energy is zero. if only the gravitational force of the earth were to act on it (i. e., neglect the forces from the sun and other solar system objects), the spacecraft would eventually crash into the earth. the mass of the earth is me and its radius is re. neglect air resistance throughout this problem, since the spacecraft is primarily moving through the near vacuum of space.

a. find the speed se of the spacecraft when it crashes into the earth. express the speed in terms of me, re, and the universal gravitational constant g

b. now find the spacecraft's speed when its distance from the center of the earth is r=αre, where the coefficient α≥1. express the speed in terms of se and α.

Marcella is a four-year-old girl who is a victim of emotional child abuse. based on the child and family services improvement and innovation act of 2011, which action should the government take for marcella? a. the state should arrest marcella’s abuser. b. the state should find a home for marcella as soon as possible. c. the state should enforce stricter laws in the area where marcella resides. d. the state should provide medical assistance to marcella.

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.

Which pair of quantities includes one quantity that increases as the other decreases during simple harmonic motion?