84. Calculate the velocity a spherical rain drop would achieve falling from 5.00 km (a) in the absence of air drag (b) with air drag. Take the size across of the drop to be 4 mm, the density to be 1.00 × 103 kg/m3 , and the surface area to be πr2 .

a)

b)

Explanation:

Given:

a)

b)

given that:

diameter of the drop,

density of the air,

the terminal velocity is given as:

where:

m = mass

g = acceleration due to gravity

density of the medium through which the drop is falling (here air)

A = area normal to the velocity of fall

coefficient of drag = 0.47 for spherical body

the answer is 12 as i may remember

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