CH10 – Projectile
and Satellite Motion
Projectiles
Projectile Motion
Motion Revisited…
Horizontal Motion

Speed or Velocity
or velocity = distance  time
v = d / t
 Speed

Acceleration
 Acceleration
a

= velocity  time
=v/t
A ball rolling horizontally…
 Moves
friction
at a constant speed if we neglect
Motion Revisited…
Vertical Motion

Velocity
v

Distance
d

= ½ gt2
Time


= gt
t 
2d
g
Falling ball
 Falls
at a constant acceleration if we neglect air
resistance
Projectile Motion
A projectile is an object moving only under
the influence of gravity.
 No other forces are involved, other than an
initial push, hit, throw, launch, shoot, etc.
 The horizontal motion is independent of
the vertical motion.
 Projectiles have parabolic path.

Projectile Motion

Projectile Motion is a combination of horizontal
and vertical motion.

Two types of projectiles:
Horizontal
Upward
Projectile Motion – Horizontal

Horizontal Projectiles—
 Initial
velocity is only horizontal, then fall
begins (acceleration down) but horizontal
velocity does not change.
Projectile Motion – Horizontal

Horizontal (x) direction
 Initial
velocity only in
this direction
 No acceleration
 Final velocity = initial
velocity since no
acceleration
 vx = d / t

Vertical (y) direction
 No
initial velocity
 Acceleration due to
gravity (9.8 m/s)
 Final velocity depends
on time in air
 vy = gt
Projectile Motion – Horizontal
At the instant a horizontally held rifle is fired
over a lever range, a bullet held at the side of
the rifle is released and drops to the ground.
Which bullet, the one fired downrange or the
one dropped from rest, strikes the ground first?
They strike the ground at the same time!
Projectile Motion – Upward

Upward Projectiles—
 Initial
velocity is at
some angle upward,
above horizontal.
 Acceleration is down.
 Horizontal velocity is
constant.
 Range is the
horizontal distance
traveled.
Projectile Motion – Upward

Horizontal (x) direction
 Initial
velocity in this
direction
 No acceleration
 Final velocity = initial
velocity since no
acceleration
 vx = d / t

Vertical (y) direction
 Initial
velocity also in
this direction
 Acceleration due to
gravity (9.8 m/s2)
 Final velocity depends
on time in air
 vy = gt
Projectile Motion – Upward

Launch angles…
 If
the launch speed is the same but the
launch angles are different, the projectiles will
have the same range if (launch angle 1 +
launch angle 2 = 90o)
Maximum
Range at 45o
Projectile Motion – Upward
Example
The boy on the tower throws a ball 20 m downrange as shown below. What is his pitching
speed?
Questions about Projectile Motion
1.
Why does the vertical component of velocity for a projectile change
with time, whereas the horizontal component doesn’t?
2.
A rock is thrown upward at an angle. What happens to the vertical
component of its velocity (A) as it rises? (B) as it falls?
3.
A projectile falls beneath the straight-line path it would follow if there
were no gravity. How many meters does it fall below this line if it has
been traveling (A) for 1 s? (B) for 2s?