# Projectile Motion ```Projectile Motion I
9/30/13
Bellwork
What is free fall?
• The motion of an object under the
influence of the gravitational force only
(no air resistance)
Announcements
• Grades are up to date except for the
Linear Motion Tests
• Any absent work needs to be made up
by Friday 10/4/13 for the progress
report
• Before school 7:00-8:00 am;
Conference periods; also today and
Thursday after school
Throwing a ball in the air
• On the way up:
• velocity decreases
• acceleration stays the
same.
• velocity zero
• At the top of the
throw:
• acceleration stays the
same.
• On the way down: • velocity increases
• acceleration stays the
same.
Throwing a ball in the air
• The velocity changes.
• The acceleration is constant, it stays
the same 9.81 m/s/s, downward
throughout the flight.
Projectiles
• Projectiles: are objects where gravity
and air resistance are the only forces
acting
• Projectiles travel with a parabolic
trajectory (path)
Lunar Lander Example
Projectiles
• A projectile’s horizontal component is
independent of the vertical component
• The force of gravity does not affect the
horizontal component of motion
• (i.e.) What is happening left and right
does not effect what is happening up
and down
Air Resistance
• Air Resistance: A force of friction that
acts on an object moving through the air
• For projectile motion we will often neglect
or assume that air resistance is extremely
small
Projectile Terms
• Range: The distance a projectile travels
horizontally from the initial position.
• Max Height: The greatest distance a
projectile travels vertically
• Hang Time: The total amount of time a
projectile is in the air
Mythbusters
• Dropped vs. Fired Bullet
• http://dsc.discovery.com/videos/mythbuste
rs-dropped-vs-fired-bullet.html