Question: A cannon fires a shell that causes a projectile to move down the barrel at a velocity of 740 m/s. What is the speed of the normal shock proceeding down the barrel in front of the projectile if the undisturbed air in the barrel is at 101 kPa and 20°C? How fast would the projectile have to be moving down the barrel if the velocity of the shock ahead of the projectile was 2.5 times the velocity of the projectile?