A stream of water flows from the fire pump to a height of 19.6 meters. At what speed is it ejected by the pump?

Given:

H = 19.6 meters – the height to which the water jet rises;

g = 9.8 m / s – acceleration of gravity.

It is required to determine v (m / s) – the speed at which the water is ejected by the pump.

Let some part of the water of mass m be ejected by the pump. At this moment, it has kinetic energy Wkin, thanks to which it rises to the height H. Then, according to the law of conservation of energy:

Wkin = Wpot;

m * v ^ 2/2 = m * g * h;

v ^ 2/2 = g * h;

v = (2 * g * h) ^ 0.5 = (2 * 9.8 * 19.6) ^ 0.5 = 384.2 ^ 0.5 = 19.6 m / s.

Answer: water from the pump is thrown out at a speed of 19.6 m / s.