Answer:
(a) The average rainfall during the
Monsoon in
India is about 100 cm or 1 m.
Total surface area of India
Volume of rain water,
Density of water, 
Hence total mass of rain-bearing
clouds over India,
.
(b) To estimate the mass of an
elephant, consider a boat of base area A in a river. Let 
be the depth of
the boat inside water. Now move the elephant into the boat.
Again measure the depth 
of the boat
inside water.
Volume of water displaced by
elephant
According to Archimedes?
principle, mass of the elephant is
m = Mass of water displaced by
the elephant
Mass of an elephant is about 103
kg.
(c) The wind speed during a
storm can be measured by floating a gas filled balloon in air. When there is no
wind storm, suppose the balloon is at vertical height 
from the
ground. Due to the wind storm, suppose the balloon moves to position B in a
small time interval t, as shown in Fig. 2.16.
If 
is the angle of
drift of the balloon, then from right angled 
or 
Hence the wind speed during the
storm,
.
(d) First we count the strands
of hair of 
area of the
head. Then by multiplying it by the total area of the head, we can estimate the
total number of stands of hair on the head. Its order of magnitude may be as
large as 
.
(e) The dimensions of a typical
classroom are
Volume of the class room 
Now one mole of air molecules
occupy a volume of
22.4 litres or 
.
Number of molecules
in
Number of molecules in the
classroom
molecules.
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