Projectile Motion
with
Air Powered Projectiles
Presented by
Mike Horton
Advantages
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Safe Operation
Controllable
Reusable
Reliable
EASY!
Is it a Rocket?
1. Rocket:
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Carries a propellant that is expelled
and forces the rocket upward.
2. Projectile:
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Gravity is the only force that acts on it.
It is not propelled once on its trajectory.
Instructions
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Select a launching site
clear of obstructions
and preferably about
50 meters in diameter.
Attach the Arbor
Scientific air pump and
adjust the launch pad
to the desired angle.
Set the rocket in the
launch position.
Instructions
2.
Select the super, high,
medium or low thrust
washer according to
the desired altitudes.
Snap the thrust
washer onto the
launcher top.
(Be sure it snaps)
Instructions
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Push the rocket
completely onto the
launcher and attach
the nose cone.
Instructions
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Stand Sideways
to pump and
pump until the
rocket launches
automatically.
Instructions
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Retrieve the rocket and nose cone.
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Push the thrust washer out of the end of
the rocket with your thumb or finger and
repeat these steps for your next launch.
Finding Initial Velocity
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Launch the projectile
vertically.
Time its flight.
Divide by two to find
its time up.
Using g= -10m/s2, if it
took 3 seconds to
stop, it must have
started at 30 m/s.
Acc = Dv/Dt so v=at
Finding the Range
1.
2.
3.
4.
Use the launch angle to find the horizontal and
vertical components of the launch velocity.
Vy = 30 m/s (sin 60°) = 26 m/s vertically
Vx = 30 m/s (cos 60°) = 15 m/s horizontally
The last half of flight time is calculated using
Vy = Vtop + gt or 26 = 0 + 10(2.6)
Doubling that gives a full flight time of 5.2
seconds.
Using d = vxt or d = 15 x 5.2 one can find a
range of 78 meters (with many assumptions
made).
Finding the Launch Angle
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The angle of the wedge is
NOT the launch angle.
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Find the angle’s complement.
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Calculations will be correct
either way.
Alternate Method
of finding range
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Use the range equation:
Where R = range,
Θ = angle from horizon,
g = -10 m/s2, and
vo = initial velocity
R=
vo2 sin 2Θ
g
Tips from Teachers
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Do not try to catch the projectile
Do not launch the washer alone
Do the lab on a marked football field
Launch when temperatures are above 50° F
Try for a calm day
Don’t forget about air resistance. Faster
projectiles will be less accurate.
Try making a super-high washer by adding a
layer of plastic wrap under the washer
Indoor Projectile Motion
The Desktop Trebuchet provides
a fun and exciting environment for
studying energy conservation,
levers, trajectories, inertia and
forces!
The Marble Projectile Ramp
helps achieve consistent,
predictable results. Use it with
any Photogate to measure the
marble’s initial velocity.
Thank You!
www.arborsci.com
mail@arborsci.com
(800) 367-6695