Chapter 13383Q13.16Speed is maximum at closest approach. Speed is minimum at farthest distance.Q13.17Set the universal description of the gravitational force, FGM mRgXX=2, equal to the local description,Fmag=gravitational, where MXand RXare the mass and radius of planet X, respectively, andmis themass of a “test particle.” Divide both sides by m.Q13.18The gravitational force of the Earth on an extra particle at its center must be zero, not infinite as oneinterpretation of Equation 13.1 would suggest. All the bits of matter that make up the Earth will pullin different outward directions on the extra particle.Q13.19Cavendish determined G. Then from gGMR=2, one may determine the mass of the Earth.Q13.20The gravitational force is conservative. An encounter with a stationary mass cannot permanentlyspeed up a spacecraft. Jupiter is moving. A spacecraft flying across its orbit just behind the planetwill gain kinetic energy as the planet’s gravity does net positive work on it.
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