Transcript Unit Two Chapter 3, Part 2 Projectile Motion

Unit Two
Chapter 3, Part 2
Projectile Motion
A projectile is an object upon
which the only force acting is
gravity
Realize…….
that the only force acting
upon an upwardly moving
projectile is gravity.
Don’t be fooled by the common
misconception that a force is
required to keep an object in
motion. A force is not required to
keep an object in motion. A
force is only required to
maintain an acceleration.
Or….. Without gravity, you could
launch a banana straight at a
monkey in a tree.
Notice: the monkey does not fall
when he catches the banana
because there is no gravity
But with gravity……
In the presence of gravity, the
monkey also accelerates
downward once he lets go of
the limb. Both banana and
monkey experience the same
acceleration since gravity
causes all objects to accelerate
at the same rate regardless of
their mass.
Gravity is the downward force
upon a projectile which
influences its vertical motion
and causes the parabolic
trajectory which is characteristic
of all projectiles.
Characteristics of Projectiles
1. Projectiles always maintain a
constant horizontal velocity
(neglecting air resistance)
2. Projectiles always
experience a constant
vertical acceleration of 10.0
m/s2 downward. (neglecting
air resistance)
3. Horizontal and vertical
motion are completely
independent of each other.
Therefore, the velocity of a
projectile can be separated
into horizontal and vertical
components.
4. For a projectile beginning
and ending at the same
height, the time it takes to
rise to its highest point
equals the time it takes to
fall back to its original
position….
5. Objects dropped from a
moving vehicle have the
same velocity as the moving
vehicle.
The distance any projectile goes
is:
d = 5
2
t
So when we are measuring the
distance we are measuring
downwardness and
sidewaysness of the projectile
Satellites –
projectile traveling fast enough
to fall around the earth rather
than onto it.
Launch Speed less than 8000 m/s
Projectile falls to Earth
Launch Speed less than 8000
m/s Projectile falls to Earth
Launch Speed equal to 8000 m/s
Projectile orbits Earth - Circular
Path
Launch Speed greater than 8000
m/s Projectile orbits Earth Elliptical Path