One day all the students of class IX were performing physics experiments in the science laboratory. Just then, the physics teacher, Mr. Vinay, came to the laboratory with a sheet of tin weighing about half a kilogram. Mr. Vinay gathered all the students and in their presence put this sheet of tin in a big tub of water. The sheet of tin sank in water and settled at the bottom of tub. Mr. Vinay now turned to the students and asked who could transform this sheet into the simplest form (or shape) which would float in water. He allowed them to use any other required tools/materials from the laboratory for this purpose. Mohan offered to make an appropriate object from this tin sheet which could float in water and not sink. He took just half an hour to make this object. The teacher placed this object in the same tub of water. It started to float in water. The teacher was very happy. He appreciated the effort made by Mohan.
(a) Why did the sheet of tin sink in water?
(b) What do you think is the simplest form of object made by Mohan from this tine sheet which could float in water?
(c) Why do you think the above object made from tin sheet floats in water?
(d) Name two modes of transport used in rivers and seas which work on the same principle as the tin sheet object made by Mohan.
(e) The tine object made by Mohan was placed, turn by turn in a tub of oil and glycerine. In which of these two liquids, the tin object will float with a greater part of it immersed inside the liquid than water and why?
(f) What values are displayed by Mohan in this episode?

Explanation

(a) The sheet of tin sinks in a water because the density of tin is greater than that of water.
(b) Mohan may have made a water-proof box from the tin sheet (by using appropriate cutting tools and sealing materials). This hollow box made of the same tin sheet floats in water.
(c) The hollow tin box contains a lot of air in it. Air is a very, very high light substance. Due to the presence of a lot of air in it, the average density of tin box becomes less than the density of water. And due to less average density than water, the hollow tin box floats in water.
(d) Boats and ships are the two modes of transport used in rivers and seas which float in water on the same principle as the hollow tin box made by Mohan.
(e) The tin box will float with its greater part immersed in oil (than in water) because oil has a lower density than water. Due to its lower density than water, oil exerts less upward (buoyant) force on tin box due to which it will sink more in oil (than water) and then float in it.
(f) The various values displayed by Mohan in this episode are (i) Awareness of Archimedes' principle (ii) Knowledge of factors affecting buoyant force (like volume of solid object immersed in a liquid and density of liquid) (iii) Application of knowledge in solving problems, and (iv) Accepting challenge (to do a job).