View Feed
Coffee Room
Discuss anything here - everything that you wish to discuss with fellow engineers.
12831 Members
Join this group to post and comment.

With all the IPL going - here is a spinning Ping Pong Ball

A fairly safe cryogenic reaction engine.
Kaustubh Katdare
Kaustubh Katdare • Apr 30, 2012

Just wondering what makes the ball spin?
Harshad Italiya
Harshad Italiya • Apr 30, 2012

Just wondering what makes the ball spin?
Some chemical trick ! Not sure . 😕
Kaustubh Katdare
Kaustubh Katdare • Apr 30, 2012
Some chemical trick ! Not sure . 😕
Never took interest in Chemistry. 👎
manishks • Apr 30, 2012
We can convert a ping pong ball into a hero's engine by poking two holes tangentially to surface of ball. Then drop it into a liquid nitrogen and hold it under surface for few seconds. As air in ball cools pressure in ball drops and some liquid nitrogen is forced into ball due to atmospheric pressure. Now take the ball out and put it on table. As nitrogen boils and discharge ball spins rapidly!!
ISHAN TOPRE • Apr 30, 2012
The spinning is rather simple and there is no black magic as someone may suggest.

The spinning is because of boiling Nitrogen. If you observe the video closely the ball has holes in it. In normal condition, the volume in the ball is occupied by atmospheric air. Now when you dip it in Liquid Nitrogen and take it out, the volume is partially filled by Nitrogen. The N2 boils and it shoots out of the holes thus we get spinning.

The important thing to not is that, at how much volume of liquid N2 are we getting 10,000RPM. It will last how much time and if applied in some weight carrying operations (like automobiles/ robots), what will be its payload capacity?

Also, this demonstration reminds me a lot of Ajeet.
His famous dialog,


Liquid isse jine nahi dega aur Oxygen isse marne nahi dega
Translation: Liquid will not let him live and Oxygen will not let him die.
manishks is right as also issue. liquid nitrogen gets into the ball through a hole pricked in the ball. However, the hole should be as tangential as possible. After that the behaviour is rather trivial. It is rocket science (at a very basic level). Dr.Kalaam will turn up his nose at it.

Share this content on your social channels -