AST101_fall2011_lecture7_oct4_v1

# AST101_fall2011_lecture7_oct4_v1 - Tides Tides Acceleration...

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Unformatted text preview: Tides Tides Acceleration of Gravity We found F g =G ME MR d 2 and F g = M R a g Hence, a g =G ME d 2 With d = RE , a g =9.8 m/s 2 Earth: 9.8 m/s2 Tides in orbit around Earth Tides a head = G afeet = G ME =8.6115701 m / s ( 6800 km)2 ME =8.6115758 m / s 2 ( 6800 km −2 m ) 2 2 Δ a = 0.0000057 m / s 2 Note: you do not have to reproduce this! Tides around Jupiter Tides (M=0.001 Msun, R=0.1 Rsun) a head = G afeet = G 0.001 M sun ( 105 km )2 0.001 M sun 7 = 1.32666× 10 m / s 6 =1.32693 ×10 m / s 5 2 ( 10 − 10 km ) Δ a = 2.7×103 m / s 2 2 2 Shoemaker-Levy 9 Shoemaker-Levy Shoemaker-Levy 9 Shoemaker-Levy Shoemaker-Levy 9 Shoemaker-Levy Morbid Quiz (not for marks) Morbid If you want to see a black hole from the inside, If is it better to pick a stellar-mass one or is a supermassive black hole? A stellar mass one (~Msun, 3 km) A A supermassive one supermassive (~107 Msun, 3x107 km) (~10 B It doesn't matter C I have no clue D Tides in orbit around a black hole Tides (M=1 Msun, R=3.0 km) R=3.0 a head = G afeet = G M sun 13 2 13 2 =1.47407× 10 m / s ( 3 km )2 M sun = 1.47604 × 10 m / s 2 ( 3 km −2 m ) Δ a= 1.97× 1010 m / s 2 Tides in orbit around a supermassive black hole Tides (M=107 Msun, R=3.0x107 km) 7 a head = G afeet = G 10 M sun 6 2 6 2 = 1.47407 ... × 10 m / s 7 2 ( 3 × 10 km ) 107 M sun = 1.47407 ...× 10 m / s 7 2 ( 3 ×10 km− 2 m ) Δ a = 0.0001 m / s 2 Clicker Quiz (1 min) Clicker How often is it high tide? Every 24 hours A Every 24 hours 50 minutes B Every 12 hours C Every 12 hours 25 minutes D Tides Moon Sun (far away) Spring and Neap Tide Clicker Quiz (1 min) Clicker How often is it Spring tide? Every half a month Every month A Every month B Every quarter year C Every half a year D Every year E Bay of Fundy Bay Tidal Drag Fg Clicker Quiz (2 min) Tidal Drag What happens to the Moon's orbit due to the tides?Wh The distance decreases and the month shortens A The distance decreases and the month lengthens B The distance increases and the month shortens F g C The distance increases and the month lengthens D Lunar Ranging Clicker Quiz (2 min) Lunar Ranging As the Moon moves out, As What happens to Earth? What It spins down and cools down A It spins down and heats up B It spins up and cools down C It spins up and heats up D Positioning Historical Eclipses Prediction vs Observation Eclipse Timing Length of Day Clicker Quiz (1 min) Length of Day What is the final state tides lead to? The moon is ejected A The moon crashes on Earth B Day and month become the same C No final state can be reached D Clicker Quiz (1 min) Length of Day What is the final state tides lead to What Phobos month for Mars's moon Phobos? =0.31 Mars days for The moon is ejected A The moon crashes on Mars B Day and month become the same C No final state can be reached D ...
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