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Projectile Motion Section 7.2. Physics. Objectives. Recognize that the vertical and horizontal motions of a projectile are independent. Relate the height, time in the air, and initial vertical velocity of a projectile using its vertical motion, then determine the range.
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Projectile MotionSection 7.2 Physics
Objectives • Recognize that the vertical and horizontal motions of a projectile are independent. • Relate the height, time in the air, and initial vertical velocity of a projectile using its vertical motion, then determine the range. • Explain how the shape of trajectory of a moving object depends upon the frame of reference from which it is observed.
What is a projectile? • Pro – jec - tile: a body projected or impelled forward, as through the air.
Types of Projectiles • Dropped straight down. • Thrown straight up. • Thrown with a horizontal and vertical velocity. http://www.glenbrook.k12.il.us/gbssci/phys/class/vectors/u3l2a.html
Plane of Motion for a Projectile http://www.launc.tased.edu.au/online/sciences/PhysSci/done/kinetics/projmo/Image1.gif
Independence of Motion in Two Dimensions • Horizontal motion does NOT affect the vertical motion. http://www.physics.ucla.edu/demoweb/demomanual/mechanics /gravitational_acceleration/horizontal_and_vertical_ball_drop.gif
Constant Horizontal Motion • Constant Horizontal Motion • Horizontal motion is constant because it is initiated by a contact force. • Vertical motion is not constant because it is caused by a long-range force.
How do we draw a projectile’s motion? • Horizontal and vertical arrows indicate respective velocities: vx & vy. • The velocity vector is the combined vector of the x and y components. http://www.staff.amu.edu.pl/~romangoc/graphics/M2/1-projectile-motion/M2-3.gif
Projectiles Launched Horizontally • Projectiles launched horizontally have no initial vertical velocity. • Their vertical motion is identical to that of a dropped object. • Downward velocity increases regularly because of acceleration due to gravity.
No Initial Vertical Velocity http://ali.apple.com/ali_media/Users/1000477/files/jpegs/curve.jpg
Practice Problems • Pg 158 • 9-11
Projectiles Launched at an Angle. • When a projectile is launched at an angle, the initial velocity has vertical and horizontal components. • Starts with highest vertical velocity, reaches its peak where velocity is zero, and descends with increasing speed.
Projectiles Launched at an Angle • Maximum height: height of the projectile when the vertical velocity is zero and the projectile has only its horizontal velocity component. • Range, R: horizontal distance the projectile travels. • Flight-time: time the projectile is in the air.
Projectiles Launched at an Angle http://www.mcasco.com/images/projm.gif
Practice Problems • Pg 160 • 12-13
Air Resistance and Projectiles • Air resistance affects projectiles. • Golf ball dimples. • Spin of a Baseball due to laces. • Frisbee. • Boomerang. http://www.fi.edu/wright/again/wings.avkids.com/wings.avkids.com/Book/Sports/Images/boomerang.gif