Projectile Motion
Vertical Motion (y-axis)
• Object motion is in free fall
• Acceleration (a) is a
constant -9.81 m/s2
• Initial Velocity (vi) is 0 m/s
Quiz
Horizontal Motion (x-axis)
• Acceleration (a) is 0 m/s/s
• Velocity is constant (vi = vf)
Quiz
Practice Problem
(Horizontal Launch)
People in movies often jump from buildings
into pools. If a person jumps horizontally by
running straight off a rooftop from a height
of 30.0 m to a pool that is 5.0 m from the
building, with what initial speed must the
person jump?
People in movies often jump from buildings into pools. If a
person jumps horizontally by running straight off a rooftop
from a height of 30.0 m to a pool that is 5.0 m from the
building, with what initial speed must the person jump?
Horizontal Knowns
• Δx = 5.0 m
• vi = vf = vavg
• tvertical = thorizontal
Vertical Knowns
• Δx = 30.0 m
• vi = 0
• a = -9.81 m/s/s
• tvertical = thorizontal
The Royal Gorge Bridge in
Colorado rises 321 m above the
Arkansas River. Suppose you kick a
rock horizontally off the bridge.
The magnitude of the rock’s
horizontal displacement is 45.0 m.
Find the speed at which the rock
was kicked.
A baseball rolls off a 0.70 m
high desk and strikes the
floor 0.25 m away from the
base of the desk. How fast
was the ball rolling?
A cat chases a mouse across a 1.0 m high
table. The mouse steps out of the way, and
the cat slides off the table and strikes the
floor 2.2 m from the edge of the table. When
the cat slid off the table, what was its speed?
A Pelican flying along a horizontal path
drops a fish from a height of 5.4 m. The fish
travels 8.0 m horizontally before it hits the
water below. What is the pelican’s speed?