Floating and Sinking ball | English
Channel: Arvind Gupta
Date: 2016-05-04

Today we will do some simple experiments on flotation. When I place it in water the ball simply floats. Can we sink this ball to the bottom without physically touching it? Looks impossible.  Let’s try. You will need a fish tank full of water, a plastic ball and a transparent cylindrical glass. When I place the ball in water it floats. When I press the ball downwards with my hand the ball bounces back to the surface.  This is because the up thrust of the water on the ball lifts it back. How can we sink to ball to the bottom of the fish tank without touching the ball physically? Place the inverted glass on the ball and press the glass down.  Slowly the ball will also go downwards along with the glass. Now the ball is touching the fish tank base. On lifting the glass the ball will rise to the surface. With the help of the glass I can make the ball float at any water height. See, the ball is floating on the surface, now it’s in the middle, and finally it’s at the bottom.  See this in a close-up.
We will repeat this experiment with a plastic bottle. Cut the top of the bottle and make a hole in the base. With my finger I can close and open the hole.  After closing the hole I can push the ball to the fish tank base. Now slowly, I will open the hole. The water level in the bottle will rise and the ball will also float higher and higher.  On closing the hole the ball will float in the middle. On opening the hole completely the ball will float to the surface of the water tank. Now I close the hole and lift the bottle above the water level. See the bottle filled with water is now lifted up. On opening the hole water from the bottle will drain out and the ball will float on the surface.

This work is supported by IUCAA (www.iucaa.in) and TATA Trust (www.tata.com/aboutus/sub_index/Tata-trusts)

Credits:,Ashok Rupner, Manish Jain, Pradnya Pujari, Shivaji Mane, Jyoti Hiremath, Arvind Gupta, Vidula Mhaiskar TATA Trust: Education is one of the key focus areas for Tata Trusts, aiming towards enabling access of quality education to the underprivileged population in India. To facilitate quality in teaching and learning of Science education through workshops, capacity building and resource creation, Tata Trusts have been supporting Muktangan Vigyan Shodhika (MVS), IUCAA's Children’s Science Centre, since inception. To know more about other initiatives of Tata Trusts, please visit www.tatatrusts.org