Question

If the pressure reading of your pitot tube is 15.0 mm hg at a speed of 200 km/h, what will it be at 700 km/h at the same altitude?

Answer 1

Note that
1 mm Hg = 133.32 Pa
1 km/h = 0.27778 m/s

1st reading:
pressure, p1 = 15.0 mm Hg = 15*133.32 = 2000 Pa
velocity, v1 = 200 km/h = 200*0.27778 =  55.556 m/s

2nd reading:
Let pressure = p2 Pa
velocity, v2 = 700 km/h = 700*0.27778 =  194.45 m/s

Apply Bernoulli's equation.
v1^2/(2g) + p1 = v2^2/(2g) + p2
p2 = (v1^2 - v2^2)/2g + p1
     = (55.556^2 - 194.45^2)/(2*9.8) + 2000
     = 228.35 Pa
     = 228.35/133.32 mm Hg = 1.713 mm Hg

Answer:  1.7 mm Hg (nearest tenth)