Projectile Motion

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Projectile Motion
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What is projectile motion?

• Projectile motion is a form of two-dimensional
  motion in which a projectile is under the
  influence of gravity.
• There is motion in both the horizontal plane
• (x-axis) and the vertical plane (y-axis).

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What is a projectile?

• Projectiles are objects that are launched into
  the air.
• Ex. balls, arrows, long jumpers

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Projectile motion

• The path in which a projectile travels is a
  parabolic curve (assuming there is no wind
  resistance).

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Projectiles vs. Free Falling Objects
Projectiles fall at the same rate as free falling
objects.
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Solving for projectile motion

• Since projectiles travel in both the horizontal
  and vertical planes, we can solve for the X and Y
  components.
• We can use the one-dimensional motion equations
  to solve for variables involved in
  two-dimensional motion problems.

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Projectile Motion
x-Motion y-motion Vavg
?x/?t ?y ½ (vi vf) ?t
g (vf - vi) / ?t
?y vi ?t ½ g?t²
vf² vi² 2g?y
The same equations we used in 1-D motion! The
trick is to solve for x and y motion of 2-D
moving objects independently!
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Projectile Motion

• Two types of projectile motion situations
• 1. Horizontally launched projectiles
• 2. Projectiles launched at an angle

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Horizontal Projectile Motion
What am I going to do about book checks???
A VERY TALL BUILDING
CRASH!!!
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Sample Problem
The Royal Bridge in Colarado is 321 m above the
Arkansas River. If you kick a rock horizontally
off the bridge and it hits the water with a
horizontal displacement of 45 m, what is the
velocity at which the rock was kicked?
?y ½(g)(?t)²
g -9.81 m/s²
8.10 s ?t
?x (Vx,i)(?t)
?y -321 m
?x/?t Vx,i
5.56 m/s Vx,i
?x 45.0 m