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Learn about projectile motion, including horizontal and vertical components, formulas, and problem-solving strategies in this comprehensive guide from January 4, 2017.
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Motion in Two-Dimensions Projectile Motion Notes January 4, 2017
Projectile Motion • A projectile can be anything that moves through the air after it has been given an initial “thrust” or input force • Projectiles are only under one force as they move through the air –GRAVITY! • We ignore air resistance in most cases to simply the problems • There are two general categories: • Projectiles launched horizontally • Projectiles launched at an angle
Important Facts about Projectile Motion: • Vertical and horizontal motions are independent of each other. • We can relate the height, time in the air, and initial vertical velocity of the projectile by using its vertical motion, then determine the range (x-distance) • We use basic motion equations to solve!
Horizontal and Vertical Components of Motion: Vertical Motion ONLY! Horizontal Motion ONLY! Vertical and Horizontal Motion!
Horizontal and Vertical Components: • The path of the projectile is known as the TRAJECTORY! • Dxwill stand for displacement on the x-axis or in the horizontal direction. This is also known as the range! • Dywill stand for displacement on the y-axis or in the vertical direction. This is also known as the height! • vxwill stand for velocity in the horizontal direction. • vywill stand for velocity the vertical direction.
Horizontal and Vertical Components: Starting Point of the Projectile Motion
Horizontal and Vertical Components: x will be positive y will be positive vx will be positive vy will be positive
Horizontal and Vertical Components: x will be positive y will be positive vx will be positive vy will be positive x will be positive y will be negative vx will be positive vy will be negative
Horizontal and Vertical Components: x will be positive y will be positive vx will be positive vy will be positive x will be positive y will be negative vx will be positive vy will be negative x will be negative y will be negative vx will be negative vy will be negative
Horizontal and Vertical Components: x will be negative y will be positive vx will be negative vy will be positive x will be positive y will be positive vx will be positive vy will be positive x will be positive y will be negative vx will be positive vy will be negative x will be negative y will be negative vx will be negative vy will be negative
What about the acceleration due to GRAVITY?(The reason for the “sign” will become clear as we do examples!) - 9.81 m/s2 - 9.81 m/s2 - 9.81 m/s2 - 9.81 m/s2
Projectile Motion Basic Formulas: • Dx = vxi t • Dy = vyit + ½ at2 • Where: • Dx is horizontal displacement • Dy is vertical displacement • vxi is horizontal initial velocity • vyi is vertical initial velocity • t is the time in flight • a is the acceleration, usually gravity!
This is Splat the Cat R.I.P Splat the Cat’s days are numbered….Why??
Projectiles Launched Horizontally • Splat the cat is tossed horizontally at 20 m/s • off a cliff that is 50 m high. • How long is the Splat in the air? • b) How far (THE RANGE) from the base of the cliff does Splat land?
Problems Solving Strategy • 1. Write known and unknown variables • 2. Write variables for x and y directions • 3. Find TIME first! What’s missing? ay = g = -9.81m/s2 y = 0 vyi = 0 ax = 0 vxi = 20 m/s t = ? y = -50 m x= ? x= 0
Your Turn: • A plane that is moving 200 m/s drops a package. The package falls -1102.5 meters to the ground. • Draw a picture and label ALL of the components! • How long was the package in the air? • How far down range (Dx) did the package hit the ground?