Your friend is asked to differentiate between evaporation and boiling. What questions could you ask to make him to know the differences between evaporation and boiling? `(AS_2)`

Reaction time : When a situation demands our immediate action, it takes some time before we really respond. Reaction time is the time a person takes to observe, think and act. For example, if a person is driving and suddenly a boy appears on the road, then the time elapsed before he slams the brakes of the car is the reaction time. Reaction time depends on complexity of the situation and on an individual. You can measure your reaction time by a simple experiment. Take a ruler and ask your friend to drop it vertically through the gap between your thumb and forefinger (Fig.). After you catch it, find the distance d travelled by the ruler. In a particular case, d was found to be 21.0 cm. Estimate reaction time.

Take 2kg of ice is at - 5^@ C. Supply heat is continuously to ice. Till it starts boiling. Note the temperature every minute. Draw a graph between temperature and time using the values you get. What do you understand from the graph. Write the conclusions. ( You know that ice melts at 0^@ c and boils at l00^@C

Ganesh is a champion in cricket in his school. When he is in the ground (for practice) and he used to whirl his bat in different style. His coach was Mr. Gunalan. The coach asked Ganesh to hold the bat at its handle and roatate fastly. But Ganesh could not do as his coach said, Ganesh developed pain in his hands. Then his coach told him to rotate the bat by holding it at its mid point. When Ganesh rotated at this position, he was able to rotate the bat faster. Ganesh was surprised and asked his coach how. (i) What was coach's explanation to Ganesh ? (ii) What is Radius of Gyration ? Give an example. (iii) How moment of Inertia is related with Angular velocity ?

Answer the following questions . a. The earth's magnetic field varies from point is space. Does it also change with time ? It so , on what time scate does it change appreciably ? b. The earth's core is known to contain iron. Yet geologists do not regard this as a source of the earth's magnetism why ? c. The charged currents in the outer conducting regions of the earth's core are thought to be responsible for earth's magnetism . What might be the ' battery ' (i.e., the source of energy) to sustain these currents ? d. The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth's field in such distant past ? e. The earth's field departs from its dipole substantially at large distances (greater than about 30,000 km) what agencies may be responsible for this distortion ? f. Interstellar space has an extremely weak magnetic field of the order of 10^(-12) T, Can such a weak field be of any significant consequence ? Explain. [Note : Exercise 2 is meant mainly to arouse your curiosity . Answers to some question above are tentative or unknown . Brief answers wherever possible are given at the end . For details , you should consult a good text on geomagnetism.]