Fluid Mechanics Viscosity Question 311
Question: The average mass of rain drops is$ 3.0\times {{10}^{-5}}kg $ and their average terminal velocity is 9 m/s. Calculate the energy transferred by rain to each square metre of the surface at a place which receives 100 cm of rain in a year.
Options:
A) $ 3.5\times 10^{5}J $
B) $ 4.05\times 10^{4}J $
C) $ 3.0\times 10^{5}J $
D) $ 9.0\times 10^{4}J $
Show Answer
Answer:
Correct Answer: B
Solution:
[b] Total volume of rain drops, received 100 cm in a year by area $ 1m^{2} $ $ =1m^{2}\times \frac{100}{100}m=1m^{3} $ As we know, density of water, $ d=10^{3}kg/m^{3} $ Therefore, mass of this volume of water $ M=d\times v=10^{3}\times 1=10^{3}kg $ Average terminal velocity of rain drop $ v=9m/s $ (given) Therefore, energy transferred by rain, $ \begin{align} & E=\frac{1}{2}mv^{2}=\frac{1}{2}\times 10^{3}\times {{(9)}^{2}}=\frac{1}{2}\times 10^{3}\times 81 \& =4.05\times 10^{4}J \ \end{align} $
BETA
