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PHYSICS 50: Lecture 11.1. RICHARD CRAIG. Homework #11. Chapter 12 We will skip 12.8 12.3, 12.13, 12.23, 12.54, 12.55 Due Tuesday April 22. Today. Force of Gravity Examples Acceleration due to gravity Gravitational Potential energy Escape velocity Circular Orbits Examples.
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PHYSICS 50: Lecture 11.1 RICHARD CRAIG
Homework #11 • Chapter 12 • We will skip 12.8 • 12.3, 12.13, 12.23, 12.54, 12.55 • Due Tuesday April 22
Today • Force of Gravity • Examples • Acceleration due to gravity • Gravitational Potential energy • Escape velocity • Circular Orbits • Examples
Newton’s Law of Gravitation • There is a force of attraction between any two masses • F = Gm1m2/R2 • G is a universal constant • G = 6.67 x 10-11Nm2/kg2
Examples • Me and you • Me and earth • Three particles
Calculate gravitational variables To add forces due to multiple masses you must add vectors
Weight (skip Weight Watchers, just climb upward) • Gravity (and hence, weight) decreases as altitude rises.
Things that effect your “weight” • Altitude • Latitude • “Local” variations in rocks • Barometric pressure
Gravitational force changes densities below sea level • Just as it’s interesting to remember that all gravitational forces are calculated from the center of the planet, it’s interesting to follow the density as one proceeds from crust to mantle to core. • “Want to get away”? Consider Example 12.4 to calculate gravity on Mars.
Gravitational potential energy • Objects changing their distance from earth are also changing their potential energy with respect to earth.
Escape Velocity • If an object has enough kinetic energy to overcome the gravitational potential energy it can escape from the gravitational pull • 1/2 mv2 > GmM/R
Circular Orbit Examples • Low Earth Orbit (LEO) • Geosynchronous orbit • Moon