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