1. The problem statement, all variables and given/known data How does the altitude of an airplane affect the measurement of the velocity, when using a Pitot tube to measure the speed? The Pitot tube is horizontal, with one end open and another closed. The stagnation pressure is measured at the end of the Pitot tube, and the static pressure is the surrounding pressure. 2. Relevant equations Bernoulli, reduced to v=√((2*(p_t - p_s)) / ρ_air) , where p_t is the stagnation pressure of the Pitot tube, p_s is the static pressure of the Pitot tube and ρ_air is the air density. 3. The attempt at a solution It is common knowledge, that air density decreases as altitude increases. As the density decreases, the air resistance (friction) decreases. This will lead to an increase in velocity. Is this a sufficient answer?