Just as precise measurements are necessary in science, it is equally important to be able to make rough estimates of quantities using rudimentary ideas and common observations. Think of ways by which you can estimate the following (where an estimate is difficult to obtain, try to get an upper bound on the quantity):
the total mass of rain-bearing clouds over India during the Monsoon
Solution 1
During monsoons, a metrologist records about 215 cm of rainfall in India i.e., the height of water column, h = 215 cm = 2.15 m
Area of country, A = 3.3 × 1012 m2
Hence, volume of rain water, V = A × h = 7.09 × 1012 m3
Density of water, ρ = 1 × 103 kg m–3
Hence, mass of rain water = ρ × V = 7.09 × 1015 kg
Solution 2
The average rainfall of nearly 100 cm or 1 m is recorded by meteorologists, during Monsoon, in India.
If A is the area of the country, then A = 3.3 million sq. km = 3.3 x 106(km)2 = 3.3 x 106 x 106m2= 3.3 x 1012m2
Mass of rain-bearing clouds = area x height x density = 3.3 x 1012 x 1 x 1000 kg = 3.3 x 1015 kg.
