#### Transcript Slide 1

```Horizontally
III. _______________________Fired
Projectile:
A projectile (object) is launched horizontally
initial speed vi. from a height ______
with an __________________
.
h
air resistance
Assume no_____________________.
vi
h
The time in the air before landing
is called the ____________________.
time of flight
the range
horizontal distance traveled = _____________
dropped
Ex. Ball 1 is________________.
horizontally
Ball 2 is fired __________________
1 2
vi
at the same time
Both reach the ground ______________________
,
initial speed
mass
regardless of 2's __________________
or ________.
independent of the x motion.
The y motion is ______________
Remember:
horizontally fired projectile
The time it takes a ______________
equal to
to fall is ______________
the time it takes a
dropped
______________
ball to fall from the same height.
air resistance
With no ____________________,
only the force of
gravity acts on the object:
___________
vi
gravity
The trajectory (path)
parabola
is a________________.
opposite
Air resistance acts in the direction _____________
decreases
to its velocity. This ___________________
its range.
vi
air resistance
gravity
no
The trajectory is _____
longer
___________
a parabola.
1.Since the object moves in 2 dimensions, each
d, v and a must be replaced by their components:
dx, vx, ax
For x motion: d, v, a  _______________
dy, vy, ay
For y motion: d, v, a  _______________
gravity ,
2. No air resistance  only ____________
downward
-y direction.
which is _______________
, in the ____
horizontal or x force. Because
There is no _________________
of this, the only acceleration a is purely vertical:
-9.81 m/s2
ay = ___________
0
ax =____________
horizontal
3. The initial velocity is purely _________________:
component
viy = ___________
(initially, no y _______________)
0
vix
vi = ________
("horizontally fired")
Horizontal (x) motion:
ax =______
0
displacement: d = v t + ½ at2
i
dx = vixt + ½axt2
=0
d =v t
x
dx
ix
dx =
velocity:
vf = vi +at
vfx = vix + axt
=0
vfx = vix
t
vfx
vfx =
uniform
The x motion is _________________.
t
Vertical (y) motion:
2
0
-9.8
m/s
viy = ____ & ay = __________
displace2
d
=
v
t
+
½
at
i
ment:
dy = viyt + ½ayt2
dy = =0 ½(-9.8)t2
|dy|
dy = -4.9t2
velocity:
vf = vi +at
vfy = viy + ayt
vfy = 0 + (-9.8)t
vfy = - 9.8t
t
|vfy|
t
dropped ball
The y motion is same as for a _________________.
Horizontal (x) motion:
Vertical (y) motion:
uniform motion
•____________
accelerated
•______________motion
constant x-speed
•____________
• same as for a ball
dropped from rest
____________________
dx = vixt
dy = -4.9t2
vfx = vix
vfy = - 9.8t
ax = 0
ay = -9.8 m/s2
Ex. A 68-kg clown is fired from horizontal cannon
with an initial speed of 40. m/s from a height
of 25 m. What is her time of flight?
40. m/s
25 m
Given:
m=
vix =
viy =
ay =
ax =
dy =
Unknown: t
68 kg
40. m/s
0
-9.81 m/s2
0
-25 m
Equation:
dy = -4.9t2
-25 = -4.9t2
5.1 = t2
2.3 s =
t
What is her range?
dx = vixt  dx = (40.)(2.3)

dx = 82 m
What is x-component of her velocity after 1.5 s?
40. m/s
What is her acceleration after 1.5 s? -9.8 m/s2
down
Recalculate the new time of flight and range if
80. m/s.
she is fired with an initial speed of ____________
Time of flight:
same
range:
dx = vixt
dx = (80.)(2.3)
dx = 180 m
Ex. A dart fired horizontally strikes a target a
distance of 0.15 m below where it is aimed.
0.15
m
blow gun
What was its time of flight?
viy = 0
ay = -9.81 m/s2
Given:
ax = 0
dy =
-.15 m
Equation:
dy = -4.9t2
-.15 = -4.9t2
0.17 s = t
Unknown: t
If the target was 9.0 m away from the gun,
what was its initial speed?
dx = vixt
 9.0 = vix (0.17)  vix = 53 m/s
horizontal motion -___________
uniform
dropped ball
vertical motion – ______________
combined motion -________________
parabola
vi
1s
2s
3s
4s
1s
2s
3s
a=
-9.8 m/s2
4s
Look at how the velocity changes:
vi
1s
2s
3s
4s
1s
2s
3s
4s
constant
The x-component of v is ________________
decreases
The y-component of v __________________
Resultant velocity  magnitude (speed) ______________
increases
tangent
___________________to
trajectory
What if it was fired with half of the original vi?
vi 1 s 2 s
3s 4s
1s
2s
3s
4s
Both fall at the same rate, which equals the
rate at which a dropped ball falls.
Which ball has the greatest acceleration?
Open your 3-ring binder to the