VACUUM BAZOOKA
Presenter: Tony Wayne, Albemarle High School, twayne@albemarle.org.
Va. SOL:
PH.7 The student will investigate and understand properties of fluids. Key concepts include
density and pressure.
National Standards:
Fluids and pressure
Topic/Concept
Shows that pressure exerts a force
and balance of pressure
Materials
Vacuum Bazooka
Ping Pong ball
Vacuum pump
3” wide sealing tape
(Staples)
Screw driver
Safety Considerations
The bazooka shoots a ping pong ball in excess of 600 mph!!! Don’t have anyone stand
in front of it. Have a everyone stand far away. It will bounce off the wall it hits. It you
drop or damage the pipe in ANY way. Get a new pipe. Irregularities, nicks and cracks
can cause the pipe to implode and send pieces flying. Inspect the pipe before creating
the vacuum.
The initiation of the vacuum release is loud. Everyone should protect his or her ears.
When dealing with vast differences in pressure, there is always a risk of implosion. BE
SAFE. Always think of the students’ safety first. Keep the students far away from the
pipe. Use it at your own risk. ( I assume no responsibility for your use of this design
since I cannot oversee it’s safe use or construction. )
Presentation
Get a student volunteer to place the pingpong ball in the front of the bazooka. It will roll
down the pipe until it hits the air stem inside. Place a piece of 3” sealing tape across the
front and another piece against the rear. It needs to make a tight seal. Aim it towards a
sturdy wall. Not towards a door, window or student. Pull the sides of the tape down on
the pipe to hold it in place. Connect the vacuum pump. Keep your fingers away from the
front and rear of the pipe now. You don’t want it to accidentally fire and do damage to your
fingers or students. To “fire” the bazooka, stab the tape at the rear end with a
screwdriver. It will ricochet off the wall it hits and make a VERY loud noise Then give
the student worksheet to the students. It is a problem based on this demonstration.
version 2.0
vip.vast.org
Vacuum Bazooka
2
How the physics is demonstrated
When the student removes her hand. The pressure is unbalanced. The 1 atmosphere of
pressure at the rear of the bazooka pushes the ball forward.
Construction and Tips Regarding the Demonstraton
The bazooka is made from a piece of strong PVC pipe the same diameter at ping pong ball.
The pipe can be found at a hardware store. It costs about $3 (2004 price). You must buy a
schedule (SCH) 40 piece of PVC pipe. The “schedule” describes the pipes thickness. The
walls of the pipe must be at about .“ thick or greater. If you get a thinner walled pipe, it may
IMPLODE under the pressure. Take a pingpong ball with you and look for a thick walled pipe
that the ball snugly fits in. Mine is a 5 foot long pipe.
You will need to make a stem for the hose. You will need a 1 3/4“ piece of CPVC pips about .”
in diameter, a CPVC 90° elbow to fit the CPVC and a brass fitting for the hose to slide over.
Glue the pieces together with CPVC cement. WARNING: This stuff can kill you. Use it outside.
Using it in a sealed room can stop your heart. Read and
heed the warnings! Drill a hole about 6 inches from the
rear of the 5’ PVC pipe. The hole should accommodate
the CPVC pipe –but not the elbow connector. If you drill
a hole that is too big, get a new piece of PVC pipe and
start over again. Do not make the connection piece fit, if
the hole is too big. It can be dangerous when you draw a
vacuum in the pipe Glue the pipe in the hole. Any air
leaks can be sealed with hot glue.
Finished.
vip.vast.org
Vacuum Bazooka
3
Here is a calculation you can do. I give this out as a student handout.