Saurabh is a student of class IX whereas his younger brother Ashu studies in class VI. During the summer holidays, Saurabh and Ashu went to visit their uncle who lives in a village. Their uncle has a big mango orchard near the village which has produced a bumper crop of mangoes this year. On the way to village, Saurabh purchased a catapult (gulel) from a shop because he enjoys felling ripe mangoes from the mango trees of orchard with the help of catapult. On reaching his uncle's mango orchard, Saurabh gave a tiny piece of stone to Ashu and asked him to put it in the catapult and hit any mango on the tree. Ashu tried to throw away the stone with catapult without stretching the rubber strings of catapult. Due to this, the piece of stone fell down to the ground instead to reaching the mango on the tree. Saurabh then taught Ashu how to use the catapult properly. By using this catapult any tiny pieces of stones, Ashu was now able to fell many ripe mangoes from the orchard trees. Ashu then saw a beautiful bird sitting on the branch of a mango tree. When Ashu was aiming the catapult at the bird, Saurabh snatched the catapult from his hands quickly and scolded him. Meanwhile, Saurabh's uncle also reached to orchard. He was happy to see Saurabh and Ashu enjoying the mangoes which they had felled from the orchard trees.
(a) Which types of energy is possessed by the stretched rubber strings of a catapult?
(b) How do the catapult strings get this energy?
(c) What energy transformation takes place when the stretched rubber strings of catapult throw away a piece of stone?
(d) Why did the piece of stone just fall down when Ashu tried to throw it away without stretching the rubber strings of catapult?
(e) When a mango attached to the trees is hit by a piece of stone thrown by catapult, the mango falls down. Which force causes mango to fall down?
(f) Why did Saurabh prevent his brother Ashu from aiming catapult at the bird?
(g) What values are displayed by Saurabh in this episode?

Explanation

(a) The stretched rubber strings of a catapult posses 'elastic potential energy'.
(b) When we do work in stretching the rubber strings of catapult, then the work done by us gets stored in the stretched rubber strings in the form of elastic potential energy.
(c) The stretched rubber strings possess elastic potential energy whereas the piece of stone thrown away by it possesses kinetic energy. So, the energy transformation taking place is:
Elastic potential energy `rarr` Kinetic energy
(d) The unstretched rubber strings of catapult do not possess elastic potential energy due to which the piece of stone is not thrown away, it just falls to the ground by the action of gravity.
(e) The force of gravity causes mango to fall down.
(f) Saurabh prevented his brother Ashu from aiming catapult at the bird because he did not want the bird to get injured or killed.
(g) The values displayed by Saurabh in this episode are (i) Adventurous nature (because he went all the way to village to enjoy orchard mangoes) (ii) Helping nature (because he taught his younger brother the proper use to catapult), and (iii) Protection of wildlife (because he prevents his brother from injuring or killing the bird).