Q. A river of salty water is flowing with a velocity $2\ ms^{- 1}$ If the density of the water is 1.2 g/cc, then the kinetic energy of each cubic metre of water is
A) 2.4 J
B) 24 J
C) 2.4 KJ
D) 4.8 KJ
Explanation
(c) Given, velocity of river,(v)=2m/s
Density of water p=1.2 $gcc^{- 1}$
Mass of each cubic metre
$\ \ \ \ \ \ \ \ \ \ \ m = \frac{1.2 \times 10^{- 3}}{\left( 10^{- 2} \right)^{3}} = 1.2 \times 10^{3}\ kg$
$\therefore$ kinetic energy$= \frac{1}{2}mv^{2}$
$\ = \frac{1}{2} \times 1.2 \times 10^{3} \times (2)^{2}$
$= 2.4 \times 10^{3}\ J = 2.4\ KJ$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.