Wednesday, July 21, 2010

Ping Pong Ball Magic!

Now this summer vacation is the time for doing some weird and interesting scientific experiments. 
Just take a ping pong ball and use a long straight pin to puncture it so that there is tangential hole on it.
Now take a beaker full of liquid nitrogen and use tongs to immerse the ping pong ball into beaker so that it stays in the middle of the beaker, for 1 minute or so.

 Take the ball out and gently place it on a table. It starts spinning at a high speed. Check the video!
Exciting to see and do, isn't it??

But why it spins?? Let's check it out~!

When you immerse the ball into liquid nitrogen, nitrogen gets inside the ball. Liquid nitrogen exists at a very low temperature of around -200 degree Celsius. When the ball is placed on the table, liquid nitrogen gets heated up and gets converted into gas. This gas rushes out at a high speed due to the high pressure inside the ball. The gas comes out through the small tangential hole with high speed. By Newton's law, the ball experiences a equal and opposite force. Any force acting on a spherical body along a tangent tends the body to spin. Hence the ball spins.

As it spins, it gets heated up due to the friction between the table and the surface of the ball . So, the speed of the ball increases for a while and the decreases as the pressure inside the ball decreases. 
Try doing this in your science lab. Sure you will like it~!
The video has been taken from the net and the picture has been taken from a site and altered for better understanding.

Discussion on this article awaited. Please post as a comment.

No comments:

Post a Comment