Transcript Projectile Motion

What is Projectile
Motion?
Instructional Objectives:
• Students will be able to:
– Define Projectile Motion
– Define Trajectory
– Characteristics of a projectile's motion
– Horizontal and vertical components of velocity
and displacement
– Initial velocity components
– Examples of problems
Projectile Motion
• A projectile is an object upon which the only force acting
is gravity. A projectile is any object which once projected
or dropped continues in motion by its own inertia and is
influenced only by the downward force of gravity
(neglecting air resistance).
• A trajectory is the path followed by a projectile. The
shape is a parabolic curve.
• -Its path is determined by gravitational acceleration.
The motion is in two-dimensions
– Vertical
– Horizontal
Types of Projectile
Motion
• Horizontal
– Motion of a ball rolling freely along a
level surface
– Horizontal velocity is ALWAYS
constant
• Vertical
– Motion of a freely falling object
– Force due to gravity
– Vertical component of velocity
changes with time
• Parabolic
– Path traced by an object accelerating
only in the vertical direction while
moving at constant horizontal velocity
Examples of Projectile
Motion
• Launching a Cannon ball
Horizontal Projectile
Equations
• X- Component
x f  xi  v xi t
• Y- Component
1 2
gt
2
 2 g y
y f  y i  v yi t 
v yf  v yi
2
2
v yf  v yi  gt
• Vectors
v xi  vi cos( )
v yi  vi sin(  )
Note: g= 9.8
m/s^2
Class Exercise
A ball is projected horizontally from the edge
of a table that is 0.862m high, and it strikes
the floor at a point 1.42m from the base of
the table.
The acceleration of gravity is 9.8m/s2.
What is the initial speed of the ball?
• Explanation:
• Choosing the edge of the table as the
origin of our coordinate system, we have
• y= viy(t) - 1/2g(t)2
•
With
•
y=-1/2g(t)2
viy
= 0 so that
Class Exercise
Cont’d
• A toy car runs off the edge of a table that is
1.066 m high. The car lands 0.5632 m from
the base of the table.
• How long does it take for the car to fall?
• The acceleration due to gravity is 9.8 m/s2.
• What is the horizontal velocity of the car?
Summary
• Projectiles travel with a parabolic trajectory due to the influence of
gravity,
• There are no horizontal forces acting upon projectiles and thus no
horizontal acceleration,
• The horizontal velocity of a projectile is constant (a never changing
value),
• There is a vertical acceleration caused by gravity; its value is 9.8
m/s/s, down,
• The vertical projectile is any object upon which the only force is
gravity,
• Vertical velocity of a projectile changes by 9.8 m/s each second,
• The horizontal motion of a projectile is independent of its vertical
motion.
Practice TIME!!!