# At what altitude does the helicopter fly if the barometer in the cockpit shows pressure p = 99.0 kPa?

**At what altitude does the helicopter fly if the barometer in the cockpit shows pressure p = 99.0 kPa? On the runway, atmospheric pressure is Ratm = 101 kPa.**

P = 99 kPa = 99000 Pa.

Rathm = 101 kPa = 101000 Pa.

g = 10 N / kg.

ρ = 1.2 kg / m3.

h -?

The barometer displays the hydrostatic pressure of the air column. The hydrostatic pressure of the gas is determined by the formula: P = ρ * g * h. Where ρ is the density of the gas, g is the acceleration of gravity, h is the height of the gas column, in our case air.

Rathm – Р = ρ * g * h1 – ρ * g * h2 = ρ * g * (h1 – h2), where h1 is the height of the air column above the runway, h2 is the height of the air above the helicopter.

The helicopter flight altitude h is the difference in altitude: h = h1 – h2.

h = (Ratm – P) / ρ * g.

h = (101000 Pa – 99000 Pa) / 1.2 kg / m3 * 10 N / kg = 166.7 m.

Answer: the helicopter flies at a height of h = 166.7 m above the surface of the runway.