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vacuum cannon drives ping pong ball at supersonic speed

by:Top-In     2020-08-08
The \"cannon\" is basically 6 feet long with a 1/2 PVC pipe.
Table tennis is placed at the proximal end, and both ends are sealed with thin plastic or aluminum foil.
The air is then drained from the pipe with a vacuum pump.
When the near-end seal breaks, the air under atmospheric pressure flows into the pipe, pushing the ball through the seal at the far end.
The key concept is that the ball travels through the vacuum in the pipe, so there is no air resistance.
With sufficient atmospheric pressure on one side of the ball and no resistance on the other side, the ball initially accelerated at a speed of about 5000 grams.
The photo shows the settings.
The only big ticket item is the vacuum pump.
The one I bought cost about $100.
The higher the vacuum, the better the result.
Ideally it should be a two-stage pump.
There are many vacuum pumps on EBay;
They are commonly used in the refrigeration industry.
Also: Schedule 40 (1 6 Feet \"safety glasses hearing protection with PVC pipe length of 1/2)important)
A 1/2 \"PVC pipe is attached to thin plastic and aluminum foil.
I used vacuum tubes and fittings of 1/4 size. Vacuum gauge (optional).
Table tennis, many of them.
Make sure that they are 40mm of the standard (1. 57\")diameter.
There are 38mm table tennis balls here;
They won\'t work very well either.
Basic shopping tools are nothing special.
This part is tricky;
The seal must be fully airtight but will break when cut
Not leaking slowly.
When they are right, they will be angry.
There are several ways.
In order to make the seal, I will list what works best for me.
It is better to clip the foil between two 1/4 plywood or medium fiber plates.
I cut a 2 \"hole in the center of the square.
Then clip it with a spring clip.
I use this seal near here.
At the far end, I stretch the foil to a pipe of 1/2 and then press the PVC coupling of 1/2 tightly on it.
Wrinkles are bad and they cause small vacuum leaks or premature breaks.
When the vacuum pump is active and sealed in place, you can expect premature rupture at any time!
I use the \"basket wrap\" plastic foil provided by the fabric store for remote sealing, and now use aluminum foil to make the square seal as shown in the following figure.
You can use plastic foil like in the photo, but I found that aluminum works best and has the highest speed.
The flat square seal works best.
After opening the vacuum pump, just keep the seal at the end of the pipe and the rest is done by vacuum.
Install hose fittings near one end of the pipe (the near end).
I used a 1/8 \"non-proliferation treaty x 1/4\" Hose Hook brass fitting.
It must be air-tight.
The sand end of the pipe is smooth and smooth.
Connect the 1/4 \"pipe between the vacuum pump and the pipe fittings.
Valves may be required depending on the type of pump;
My pump is closed. off valve. 1.
Put table tennis at the \"near\" end, just in front of the seal. 2.
Place the seal at the \"far\" end (
See photos in step 3). 3.
Set a target, aluminum cans, for example. 4.
Wear safety glasses and hearing protection. 5.
Open the vacuum pump. 6.
Keep a square seal at the Pipe opening close to the end.
The vacuum will hold it and hold it tight.
Two photos show two \"proximal\" seals held by vacuum.
I use aluminum foil here now. 7.
Wait until the maximum vacuum is reached and then puncture the Proximal Seal.
There will be a loud noise.
The main photo shows that shooting occurs when the ball is easy to pass through the aluminum tank.
The maximum vacuum is close to 30 \"of Mercury, and the ball can easily pass through two cans.
Other photos show near sealing in full vacuum. Remember -
These seals may break unexpectedly in this step.
Since I have previously made rash statements about shooting table tennis at supersonic speeds, I need to describe how these speeds are measured.
I made a \"ballistic pendulum \";
A device used to measure the initial speed of rifle bullets, but now it is mainly used in physics classes to demonstrate the principle of conservation of momentum and energy.
The projectile is shot into a block and kept inside the block.
Then, the block projectile swings due to the momentum of the projectile.
Measure the vertical height gain of the block, which represents an increase in potential energy when multiplied by the mass of the block projectile.
The velocity of the projectile is given with the following equation: velocity = (m+M)/m (√2gh)
Among them: m = the mass of the projectile, in kilograms (
Table tennis quality = 2. 7 g = 0. 0027 kg)
M m = mass of blocks, in kilograms (1. 32 kg)
G = acceleration of gravity, 9.
81 h = vertical height gain, m, only less height gain obtained from the air test. (2. 5 cm = 0. 025 m)
The numbers in parentheses are the mean of my test.
The speed of table tennis is 342 m/s calculated by the above values.
The sound speed at sea level is 343 m/s. Studies (
Eayars/publications/ajp0096. pdf)
The results show that the theoretical speed cannot exceed the speed of light.
\"The ballistic pendulum is a device for measuring [projectile\'s]
Momentum, so the velocity and kinetic energy can be calculated.
Modern time instruments can measure the speed of projectiles directly, so the pendulum is basically out of date.
Although the pendulum is considered outdated, it is still in use for a considerable period of time and leads to great progress in ballistic science.
Today, the ballistic pendulum can still be found in the physics classroom because it is simple and useful in demonstrating momentum and energy properties. ” (From Wikipedia).
The picture below shows the ballistic pendulum I made (
And my screwdriver and chisel).
The lines on the panel in the background measure the height in centimeters.
The laser indicator shows the height of the block.
In the photo, the first shows the height before shooting, and the second shows the maximum height obtained after shooting.
The camera recorded the action.
The last picture is table tennis in the block.
In addition to the momentum from the ball, there is the momentum to be transferred from the air leaving the cannon to the block.
I only run the test using air and subtract this average height (0. 03 cm)
Test with table tennis.
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