Newton’s Law of GravitationA uniform spherical shell shell of matter attracts a particles that is outside the shell as if all the shell’s mass is concentrated at its center!
G = 6.67 10–11 N m2/kg2
Superposition Principle
Gravitation Near Earth’s Surface
Gravitational acceleration
1. Earth is not uniform.
2. Earth is not a sphere.
3. Earth is rotating.
Mean Earth surface (0 km, 9.83 m/s2), Mt. Everest (8.8 km, 9.80 m/s2), highest manned balloon ( 36.6 km, 9.71 m/s2), Space Shuttle orbit (400 km, 8.70 m/s2), and communications satellite (35,700 km, 0.225 m/s2)
Kepler’s Laws
1. The Law of Orbits: All planets move in elliptical orbits, with the Sun at one focus.
2. The Law of Areas: A line that connects the planet to the Sun sweeps out equal areas in the plane of the planet’s orbit in equal times, i.e., the rate dA/dt at which it sweeps out area A is constant.
3. The Law of Periods: The square of the period is proportional to the cube of the semimajor axis of its orbit.
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