When a .22-caliber rifle is fired, the expanding gas from the burning gunpowder creates a pressure behind the bullet. this pressure causes the force that pushes the bullet through the barrel. the barrel has a length of 0.61 m and an opening whose radius is 2.8 x 10²³ m. a bullet (mass = 2.6 x 10²³ kg) has a speed of 370 m/s after passing through this barrel. ignore friction and determine the average pressure of the expanding gas.