PROJECTILE MOTION NOTES i CP PHYSICS

Preview the material 1. Big Ideas of projectile motion 2. real life application & examples of projectile motion 3. Equations Write the equation Define the variables Give the units of the variables White book pg 73-80 Blue book Ch 6

EQ: How do we describe projectile motion?

PROJECTILE DEFINITIONS projectile = an object that once launched has only gravity acting on it trajectory = path that a projectile takes through the air

two dimensional projectiles most projectiles move through two dimensions of motion horizontal (x) a force sets the object in motion in the horizontal direction once released, force can no longer act on it horizontally motion becomes uniform (constant horizontal velocity) vertical (y) only force acting in the vertical direction is gravity object moving upward will slow down (velocity decreases) object moving downward will speed up (velocity increases) horizontal and vertical motions are INDEPENDENT of each other both occur in the SAME TIME interval

horizontal projectiles projectiles that initially move only in a horizontal direction until nothing supports them and they fall to the Earth examples: ball rolling off a table, dropping an apple out of a moving car, bomb dropped from an airplane projectile’s horizontal velocity (vx) is constant from start to finish its vertical velocity (vy) starts at zero and increases to a maximum value just before the projectile hits the ground (due to acceleration caused by the force of gravity)

Horizontal projectiles

horizontal projectiles Equations: t = √[(2dy)/g] dx = vxt vf = vi + gt (Note: for y only, vi = zero) dy = ½ gt2

straight up projectiles projectiles that are thrown straight up into the air and fall down through the same trajectory example: throwing a ball up into the air and catching it, shooting a rocket straight up

straight up projectiles velocity changes through trajectory: at instant of release – has (+) maximum velocity, upward motion as approaches top – slows down due to gravity acting against it at top – velocity is zero (must stop and change direction) as approaches release point – increases due to gravity just before caught at release point – has (–) maximum velocity (same as the initial velocity), downward motion

straight up projectiles symmetrical trajectory time up = time down distance up = distance down total displacement = zero (ends back up at starting point) equations for straight up problems: (only use for ½ of trajectory) vf = vi + gt vf2 = vi2 + 2gd always known: vf = zero (at very top of trajectory) g = -9.8 m/s2 (gravity acts in down direction)

Summary 1. What are the two types of projectiles? 2. draw a diagram of their paths 3. Give an example of each situation