Question

Determine Ek. of water with volume V = 3m3, if it moves with speed v = 72km / h.

Answer 1

By definition, the kinetic energy is:

$$E_k =\dfrac{mv^2}{2}$$

where $m$ is the mass of the water, and $v = 72km/h = 20m/s$ is its speed. The mass of $V = 3m^3$ is:

$$m = 1000\dfrac{kg}{m^3}V = 3000kg$$

Thus, obtain:

$$E_k =\dfrac{3000\cdot 20^2}{2} = 0.6\times 10^{6}J = 0.6MJ$$

Answer.  0.6 MJ.