3. A normal shock wave moves into still air with a velocity of 5000 ft/sec. The still air is at 500R and 10 psia. Calculate: (a) the velocity of the air behind the wave relative to the ground (b) the static pressure behind the wave (c) the stagnation temperature behind the wave relative to the ground. 4. A normal shock wave moves down a constant-area duct containing air. The air ahead of the shock wave is at rest and at a pressure and temperature of 100 kPa and 20C, respectively. If the static pressure ratio across the shock is 2.5, find the static pressure, static temperature, stagnation pressure, stagnation temperature, and velocity (last three relative to the duct) of the air behind the shock.