ASTR 1110 book summary - ch.4.5

# ASTR 1110 book summary - ch.4.5 - Astronomy Book Notes 4.5...

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Astronomy – Book Notes 4.5 Orbits, Tides, and the Acceleration of Gravity - Three Concepts - How Orbits Can Change - How Gravity Produces Tides - The Acceleration of Gravity How Do Gravity and Energy Together Allow Us To Understand Orbits? - Orbital Energy o A planet orbiting the Sun has Kinetic Energy (its moving around the Sun) Depends on its orbital speed Gravitational Potential Energy (would fall towards Sun if stopped orbiting) Depends on its distance from Sun o Planet’s total Orbital Energy: the sum of its kinetic and gravitational potential energies Always stays the same o Orbits cannot change spontaneously - Gravitational Encounters o Orbits can change through exchanges of energy Gravitational Encounter: the two objects pass near enough so that they can feel the effects of the other’s gravity. One way that two objects can exchange orbital energy - Atmospheric Drag o Friction can cause objects to lose orbital energy o Friction may also play a role in shaping the current orbits of some moons and planets - Escape Velocity o An object that gains orbital energy moves into an orbit with a higher average altitude. o Give spacecraft enough orbital energy may end up in an unbound orbit that allows it to escape Earth completely. o Escape Velocity: The speed necessary for an object to completely escape the gravity of a large body such as a moon, planet, or star. Earth’s escape velocity = 40,000 km/hr, or 11 km/s minimum velocity required to escape Earth’s gravity if a if a spacecraft starts near the surface.

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ASTR 1110 book summary - ch.4.5 - Astronomy Book Notes 4.5...

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