Transcript Projectile Motion

Projectile Motion
Fact or Fiction
 For a fastball to travel at 90 mph, the
pitcher’s hand (or fingers) must be moving
at 90 mph when the ball is released
 The moon is constantly falling towards
Earth
 A coin dropped off a cliff will reach the
ground before another coin thrown
horizontally from the cliff at the same
height.
Projectile
 Object that is launched by a force and
continues to move by its own inertia
 Only force acting on object is gravity
 Trajectory- the path of a projectile
(parabola)
Projectile Motion
 Horizontal (x) and Vertical (y)
components are independent of each
other
 No force acts horizontally; Horizontal
motion is constant.
 Force of gravity acts vertically; vertical
motion is accelerated
What does this mean?
 Objects propelled horizontally also fall
vertically at a rate of +9.8 m/s2 (No
matter how hard object is thrown)
 Horizontally launched object and one that
is dropped
Rolling Ball off Table
If we push the ball
harder, giving it
greater ___________
velocity as it rolls off
the table, the ball
takes _____ time to
fall to the floor. Draw
the new trajectory
Rolling Ball off Table
Projectiles have 2 velocitiesHorizontal and Vertical!
 Force of gravity only acts vertically
 Vertical Velocity (Vy) - Force of gravity accelerates objects vertically
at a rate of 10 m/s2 downward. (So in the vertical direction the ball
slows down on the way up and speeds back up on the way down by
10 m/s every second)
 Horizontal Velocity (Vx)
 In absence of air resistance, projectile maintains initial horizontal
velocity it was given. (Inertia)
 Vx is constant!
 Vix = Vx = constant
 Vx = dx/t
Objects that are thrown
horizontally
 only one factor determines the time in
air.
 Object's initial height (dy)
 t in air =
dy
Objects that are thrown
horizontally
 To find the maximum range (dx) or
horizontal displacement use the formula:
 dx = vxt
Ex. A stone is thrown
horizontally at 7.5 m/s from a
cliff that is 68.4 m high. How
far from the base of the cliff
does the stone land?
 Draw a diagram of this situation
 Break up information into x and y!
 27.8 m from the base of the cliff
Ex. A baseball is thrown
horizontally with a velocity
of 44 m/s. It travels a
horizontal distance of 18 m
to the plate before it is
caught.
 A. How long does the ball stay in the air?
 B. How far does the ball drop during its
flight?
 A = 0.41 s
B = 0.82 m
What will happen if a pilot
drops a package when the
plane is directly over the
target?
The trajectory of a projectile
launched upwards looks
like...
Monkey and the
tranquilizer gun
 A scientist needs to shoot the monkey
with a tranquilizer gun, but he knows that
as soon as he shoots the gun, the
monkey will let go of the tree and fall to
the ground. Should he aim (above,
beneath, or straight at) the monkey?
 Monkey & the Hunter
Thrown at monkey with
slow speed
Thrown at monkey with
fast speed
Does the moon fall in the
sky?
Satellites are
 Projectiles that fall around Earth
 The moon is a satellite
 Geosynchronous orbits match the Earth’s
spin
Show what you know
 1. A projectile’s motion is...




a. linear.
b. one-dimensional.
c. two-dimensional.
d. three-dimensional.
 2. A projectile’s horizontal motion is...
 a. uniform (constant).
 b. accelerated.
 c. absent.
Show what you know
 3. The vertical component of a projectile’s motion
is...
 a. uniform (constant).
 b. accelerated.
 c. absent.
 4. A boy is riding a skateboard along a smooth,
flat street. If he jumps straight up off the board,
he will land...
 a. in front of the board.
 b. behind the board.
 c. on the board.