1. PROJECTILE MOTION NOTES i
CP PHYSICS

2. 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

3. EQ: How do we describe projectile motion?

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

5. 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

6. 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)

7. Horizontal projectiles

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

9. 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

10. 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

11. 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)

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