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Projectile Motion I 9/30/13 Bellwork What is free fall? • The motion of an object under the influence of the gravitational force only (no air resistance) Announcements • Grades are up to date except for the Linear Motion Tests • Any absent work needs to be made up by Friday 10/4/13 for the progress report • Before school 7:00-8:00 am; Conference periods; also today and Thursday after school Throwing a ball in the air • On the way up: • velocity decreases • acceleration stays the same. • velocity zero • At the top of the throw: • acceleration stays the same. • On the way down: • velocity increases • acceleration stays the same. Throwing a ball in the air • The velocity changes. • The acceleration is constant, it stays the same 9.81 m/s/s, downward throughout the flight. Projectiles • Projectiles: are objects where gravity and air resistance are the only forces acting • Projectiles travel with a parabolic trajectory (path) Lunar Lander Example • http://phet.colorado.edu/sims/lunarlander/lunar-lander_en.html Projectiles • A projectile’s horizontal component is independent of the vertical component • The force of gravity does not affect the horizontal component of motion • (i.e.) What is happening left and right does not effect what is happening up and down Air Resistance • Air Resistance: A force of friction that acts on an object moving through the air • For projectile motion we will often neglect or assume that air resistance is extremely small Projectile Terms • Range: The distance a projectile travels horizontally from the initial position. • Max Height: The greatest distance a projectile travels vertically • Hang Time: The total amount of time a projectile is in the air Mythbusters • Dropped vs. Fired Bullet • http://dsc.discovery.com/videos/mythbuste rs-dropped-vs-fired-bullet.html • http://www.youtube.com/watch?v=D9wQVI EdKh8