Magical Weight Gain | Marathi | Quizzical Problem
Channel: Arvind Gupta
Date: 2015-03-06

This is an amazing trick you can perform and impress your friends. It’s almost magical and counter-intuitive and you can also learn principle of flotation, sinking and buoyancy. For this all you need is a pan balance, a spring balance, half mug full of water and a piece of stone. First take a mug fill it half with water and place it on a pan balance. Notice the reading on the balance – 400gms. This will be the weight of water. Now you can ask your friends a question. What if I put my fingers inside this water and not touch the mug. Will the reading change, will it become more or less. Most of your friends might say that since you are not touching the mug it will remain at 400gms. And this is where the magic begins. Now put your fingers inside the water. Magically the weight of the water will increase. On removing the fingers the weight of water will decrease.
Not let’s try the experiment by putting our fist inside the water. We know that a fist has more volume then just the fingers. Now the weight of water will increase more. So this has to do with the volume of things which are put inside the water. To understand this phenomenon take help of a spring balance and hang a stone. Notice the reading on the spring balance. This is the weight of the stone, approximately 64gms. Weight of water is still 400gms. Now let’s put stone inside water. Let’s see what happens to the weight of water and weight of the stone when we put stone inside the water so that it is not touching any part of the mug. We will see that the stone has lost weight, just like when you go inside a swimming pool you feel lighter, stone inside the water is feeling lighter and it is lighter by about, as you can see, 26gms. In water the stone weighs 36gms less. But what happens to the water?  Interestingly, the weight of the water will increase by the same amount. 
Repeat the same experiment by using kerosene. Kerosene is lighter than water and you will see that the amount of weight that the stone looses is less in kerosene than in water. This is because the amount of loss is equal to the weight of liquid displaced. Since kerosene is lighter the weight of kerosene displaced is less than 
the weight of the water displaced and it also explains why when we dip the fist, the weight of water displaced was larger compared to when we dipped our fingers and hence when we dip the fist the weight of water increases much more than we dipped our fingers. This explains the concept of buoyancy and flotation and sinking and you can perform this magic trick. This work was supported by IUCAA and Tata Trust. This film was made by Ashok Rupner 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