Lecture 32

Lecture 32 - Last Meeting Physics 231 General University...

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1 Physics 231 General University Physics Lecture 32 Lecture 9 1 Last Meeting ± Gravity ² Field ² Energy Lecture 9 2 Today ± Gravity ² Conservation of Mechanical Energy ² Satellite Motion ² Black Holes Lecture 9 3 Lecture 9 4 Energy Diagram constant ffi i KU KU +=+ = Gravitational Potential Energy GMm U r =− Lecture 9 5 Problem:Objects falls to Earth ± A 1kg object released from rest 500km above the Earth. ± What is its impact speed on the ground? (Ignore air resistance!??!) ² 3.02km/s ± What would be the impact speed if the Earth were flat? ² 3.13km/s
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2 Lecture 9 6 Energy and Satellite Motion ± Assume an object of mass m moving with a speed v in the vicinity of a massive object of mass M ² M >> m ± Also assume M is at rest in an inertial reference frame ± The total energy is the sum of the system’s kinetic and potential energies Lecture 9 7 Energy and Satellite Motion (cont.) ± Total energy E = K + U ± In a bound system, E is necessarily less than 0 ± Special case: E=0 for a body initially at rest and infinitely far away. The K=-U at all times! ± Demo: Ball rolls down hill 2 1 2 Mm Em v G r =− Lecture 9 8 Quiz: A rock, initially at rest with respect to Earth and located an infinite distance away is released and accelerates toward Earth. An observation towers is built 3 Earth-radii high to observe the rock as it plummets to Earth. Neglecting friction, the rock’s speed when it hits
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This note was uploaded on 11/16/2010 for the course PHY 231 taught by Professor Ellis during the Spring '08 term at Kentucky.

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Lecture 32 - Last Meeting Physics 231 General University...

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