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Projectile and Satellite Motion. PROJECTILE MOTION. We choose to break up Projectile Motion as a combination of vertical free-fall motion and horizontal motion at a constant speed. Forces are at work in only the vertical motion. Parabola (approximately). Monkey in a Tree. Set to 48 minutes.
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PROJECTILE MOTION • We choose to break up Projectile Motion as a combination of vertical free-fall motion and horizontal motion at a constant speed. • Forces are at work in only the vertical motion
Monkey in a Tree Set to 48 minutes
For a particular range less than the maximum and for a particular launch velocity, two different launch angles will give that range. The two angles add to give 900. 450 gives the maximum range. Simulation
Free Fall Results • Horizontal motion is constant • No force is acting • Vertical Motion is accelerated • Gravity acts in this direction • Rise time = Fall Time • Final speed = Initial speed
FAST-MOVING PROJECTILES - SATELLITES • Let’s throw stones horizontally with ever increasing velocity. • The Earth’s curvature is 16 ft for every 5 miles (4.9 m for 8 km).
5 miles 16 ft 16 ft Throw an object faster, faster, faster. Curvature of Earth We draw in each trajectory for 1 second
Planet Sun Kepler’s Laws • First Law • Planets orbit the Sun in ellipses with the Sun at one focus of the ellipse
Ellipses d1 d2 Focus Focus d1 + d2 = constant for any point on ellipse
b a Ellipses a = Semi-major axis b = Semi-minor axis
Eccentricity c a e = c/a
Kepler’s Laws • Second Law • A line drawn from the planet to the Sun sweeps out equal areas in equal intervals of time
The Search for Order • Perfect solids
The Search for Order • Music of the Spheres
Kepler’s Laws • Third Law • The orbital period of a planet squared is proportional to the length of the semi-major axis cubed. P2µ a3
Using the Third Law P2µ a3 P2= (constant)a3 P2= a3 P measured in years, a in AU, object orbits Sun
Kepler’s Laws • Empirical • Kepler could not explain why the planets orbited the Sun (he thought it had something to do with magnetism) • Universal
m M The Apple
Moon F R Earth The Earth and Moon
The free-fall motion of a projectile near the surface of the earth is very nearly parabolic. A parabola is one of the conic sections. Ellipse Parabola Hyperbola Circle
Vescape = 7 mi/s = 11 km/s Vcircle = 5 mi/s = 8 km/s Ellipse Hyperbola Parabola Ellipse Ellipse - Circle Ellipse Ellipse
Orbiting • Falling without getting closer to the ground. • Force of Gravity = Centripetal Force