Transcript PROJECTILE MOTION NOTES i

PROJECTILE MOTION
NOTES I
CP PHYSICS
PREVIEW THE MATERIAL
. 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
•
1
• 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
• dy = ½ gt2
(Note: for y only, vi = zero)
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