27lecture2a08

# 27lecture2a08 - Physics 2A Lecture 27 Mar 11 Vivek Sharma...

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Physics 2A Lecture 27: Mar 11 Vivek Sharma UCSD Physics

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Projectile Velocity Needed To Escape Earth’s Gravity 2 E Gravity is a conservative force. Total energy of body of mass m, speed v 1G M m is v- E= + = 2 KU m r esc E Escape speed v of a body launched from earth surface (r=R ) is the minimum launch speed in order to escape earth's gravity travel to r= Body with escape velocity will have v=0 at r= K=0 & U=0 E= ⇒∞ ⇒⇒ 0 e 2 sc esc esc 1 E= m Energy Conservation E=0 at launch & all points after 2 At launch, v ; v 11200m/s !! Hence those booster rockets on shutt 0 l v 2 e E E E E GM R R GM m = = =
But You Cant Escape Everything Meet Mr. Black Hole, The Cannibal of The Universe

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Black Holes: No Escaping These Predators esc 2 v GM R = escape v from an object depends only on object's M & R esc Making an object of mass M more compact by decreasing its radiu increases velocity v needed to escape from s R it sun When a star with M >> M burns out, gravitational force between all its particles can cause star to collapse on itself causing R to drop and matter density to skyrocket ! ρ Gravitational force at the surface of such a star becomes so strong that no particle or even light can escape from it . Any object coming close to such star will be ripped apart by Bl s
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27lecture2a08 - Physics 2A Lecture 27 Mar 11 Vivek Sharma...

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